Kenworth Professional Service Workbook wo r k bo o k • N UM B E R 4 , 2014 • VO LUM E 110
T680/T880 HVAC System
T680/T880 HVAC T680/T880 HVAC System Refrigerant Flow Diagram
The purpose of the HVAC system is to keep the driver warm in the winter and cool in the summer. It also keeps the windows fog-free and is better for fuel economy at highway speeds than an open window. Kenworth has different HVAC systems installed for different model groups. The popular T680 and T880 models have the most modern system, with advanced features very similar to current production luxury cars. As a result, the HVAC system installed in the T680 and T880 operates differently from the systems in other Kenworth model groups. Drivers who are used to the HVAC systems in Kenworth’s other models may complain that the HVAC system in the T680 or T880 is not working properly when they bring the truck in for service. As a Service Technician, it is important that you are able to distinguish between a valid complaint and a misunderstanding of how the system works.
This Professional Service Workbook will describe how the new HVAC features found in the T680 and T880 models differ from the HVAC systems in other model groups: B-Cabs (T440, T470, T660, T800, W900 & C500), T700/T2000, and medium duty models K270/370, T170, T270, T370. In addition, general guidelines for servicing and charging HVAC systems will be covered as well as specific guidelines for troubleshooting the T680/T880.
How Air Conditioning Works Air conditioning works for two reasons. One is a simple principle – Heat “transfers“ is always moving from a hot place to a colder place. The other reason is chemistry. With its extremely low boiling point (-14°F), R-134a refrigerant easily absorbs heat at one end the truck cab (the evaporator) and gets rid of heat at the other end (the condenser).
©2015 Kenworth Truck Co., A PACCAR Company This workbook has been prepared with materials provided to Kenworth Truck Company by its OEM supplier for the product featured. Produced by Burgio, Cooney & Associates, Independence, MO. This publication may not be reproduced without the written permission of Kenworth Truck Company. Phone: 816-353-3672 • Fax: 816-353-4206 • e-mail: [email protected]
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T680/T880 HVAC Inside the evaporator, refrigerant draws heat out of the cab and lowers the air temperature inside. The condenser gives off the heat from the refrigerant into the outside air. Between these two ends, the refrigerant circulates, acting like a conveyer belt for heat. When air conditioning doesn’t “blow cold,“ one or more of the components are not allowing heat to transfer properly.
Air Conditioning Operation •
The A/C COMPRESSOR moves the refrigerant through the system, either by pushing it under pressure or pulling it with suction. It draws cool R-134a vapor from the evaporator, compresses it into a hot, high pressure vapor, and then discharges it to the condenser. A belt-driven electric clutch engages the compressor when the air conditioning system is on. The CONDENSER is like a radiator for refrigerant. The hot R-134a vapor travels through the thin tubes and heat is transferred from the refrigerant to the fins. The cool ram air, flowing past the fins, transfers the heat to the air. Without the heat to maintain it as a vapor, the R-134a condenses back into a liquid. The RECEIVER/DRYER is the only component that does not change the refrigerant’s state. The receiver/dryer removes damaging water and contaminants from the refrigerant. The receiver/ dryer also stores refrigerant so the expansion valve can deliver a steady supply to the evaporator, which demands different amounts of refrigerant depending on the operating conditions. The EXPANSION VALVE regulates refrigerant flow to assure a steady supply of cold refrigerant needed by the evaporator to absorb cab heat. As liquid refrigerant exits the high pressure valve into the EVAPORATOR, refrigerant pressure drops rapidly. The refrigerant vaporizes, absorbing heat from the cab’s interior air. It then is drawn into the compressor to start the cooling cycle again. During system operation it may be necessary for the engine fan and the A/C compressor to turn on and off. There are SENSORS that monitor the system that controls these components. For T680/T880, when in AUTO mode, additional
Expansion Valve Opened and Closed
sensors are used to determine how the ventilation system will operate given the temperature selected on the control head. The REFRIGERANT, R-134a, absorbs and gives up heat as it circulates through the refrigerant lines. The refrigerant system is charged by weight – that is, only so much is added to achieve best performance. Since the technician doesn’t know how much R-134a is still in the system, the entire system must be evacuated first, then recharged to the correct weight.
Please refer to the Model Group’s Service Manual for specific procedures.
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T680/T880 HVAC Dash
Model T680/T880 HVAC Controls
New T680/T880 HVAC Features
Now that we’ve reviewed the basic operation of air conditioning, let’s focus on some of the new HVAC features found in the T680/T880 models:
There are separate HVAC controls for the dash and, if equipped, the sleeper.
1. Fan Control Dial turns clockwise from OFF to HIGH. Eight different fan speeds can be selected. The Air Flow Control directs the air flow through vents in the middle of the dash, at the top of the dash for defrosting, and near the floor. 2. AUTO Mode Button– when pressed: the control head computer determines how to control air flow and fan speed to meet the temperature selected by the driver via the temperature knob on the control head. NOTE: While in AUTO mode, the LED lights on the Fan Control and Air Flow Control knobs change color indicating the HVAC computer is controlling these two functions.
• • •
The new dash control unit now communicates on a new J1939 data bus exclusive to the T680/T880’s C-CAN. Five new actuators control the system, all of which are the same part number and can be swapped and easily tested with the Electronic Service Analyst (ESA) tool. New blower motor has the fan speed control (Linear Power Module) built into the unit. All Kenworth sleeper HVAC systems still use resistors, 2 or 3, to control fan speed. A single pressure transducer on the High Pressure line replaces the A/C line High Pressure, Low Pressure and Fan Control pressure switches. The HVAC system can be diagnosed with the ESA tool. The new cab HVAC Filter. The fresh air intake module is built to receive a standard air filter and one of two optional filters: the micro particulate or ember filter. The micro particulate air filter is for those customers in dusty environments. The ember filter is for those in hazardous environments. The recirculated air supply has a mesh air filter located behind the dash. The sleeper HVAC unit has a standard air filter. It is the same part number as the cab HVAC fresh air supply filter.
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If the operator moves either control knob, the LED lights change back and the computer stops controlling the function. If both knobs are moved, the AUTO button LED turns off. 3. Temperature Control Dial turns clockwise for heat, counter clockwise for cool. Selected temperature is compared to actual cab temperature as measured by the cabin temp sensor below and to the right of this dial. 4. Max Defrost Button – when pressed, sets fan speed to maximum, air flow to defrost, enables the A/C Compressor and sets the mode door for maximum heat.
T680/T880 HVAC 5. Air Distribution Dial controls where the air will be distributed: dash and floor, dash, floor and defrost, defrost or floor. 6. Sleeper Enable Switch (only for vehicles with a sleeper) turns the sleeper control panel ON/ OFF (the centered green light illuminates). 7. Temperature Sensor – senses the temperature in the cab. 8. Air Conditioner Button – allows the A/C compressor to cycle if necessary (the centered green light illuminates). It is automatically turned ON when the Air Flow Control Dial activates Defrost. NOTE: The Fan Control (1) must be ON. 9. Fresh Air/Recirculation Button – controls the source of air flow. In Fresh Air mode, air comes from outside the cab. In Recirculation mode, an amber light in the dial signals that air is coming from inside the cab. Fresh Air automatically turns ON when either Defrost or Floor and Defrost is selected on the Air Flow Control Dial.
Basic Troubleshooting Air Conditioning Systems In general, air conditioning is extremely reliable most of the time. When something goes wrong, the odds are it could be something simple. Remember that one malfunctioning air conditioning component can make another one stop working. Take a “tour“ of the complete system, making notes of problems as you go. Don’t try to fix problems as you encounter them. Make a complete list. A technician can spend 20 minutes fixing a leaky compressor fitting, only to discover that the compressor itself is bad – not an efficient use of time. The first step to troubleshooting any A/C system is to perform a visual inspection. 1. Confirm the ignition is turned off and inspect the A/C components for any visual damage, leaks, etc. Look particularly for oil at joints, at the compressor, and the Thermal Expansion Valves (TXV).
Sleeper Controls (If Equipped) 1. Fan Control Dial – four different fan speeds. It shares refrigerant with the cab unit, but delivers cooling air through its own expansion valve and evaporator. The expansion valve is under the sleeper unit. All air from the sleeper blower passes through the evaporator, then is split by the temperature door, sometimes called a blend door. Some air bypasses the heater core, some passes through the heater core. There is no valve on the heater core. 2. Temperature Control Dial – A sensor inside the sleeper HVAC ducting measures and adjusts sleeper air temperature. NOTE: The sleeper controls will not function unless the Dash control sleeper override switch (6) is pressed. 3. Air Conditioner Button – The cab A/C switch will be turned on automatically if A/C is selected on the sleeper control panel. The cab fan also will be turned ON low speed automatically (if it was OFF). Now that you’re familiar with differences between the dash controls of the cab unit and the sleeper control operation, let’s review how to troubleshoot the air conditioning system in general and then descibe how to troubleshoot the HVAC system of the T680/ T880 in particular.
2. Check and/or replace the fresh air filter as necessary. 3. Make sure that nothing is blocking the condenser airflow. Be sure to review the space between the heat exchangers. 4. Carefully clean the condenser with a mild detergent and water. Dry with shop air being careful not to damage the fins of the condenser. 5. With the engine now running let the A/C run for a few minutes. Verify that the compressor engages with the pulley and clutch plate rotating at the same speed (not slipping). 6. Verify that the engine fan engages after approximately five minutes of A/C operation. Volume 110, 4/2014 | Professional Service Workbook | 5
T680/T880 HVAC 7. The sunload sensor should not be blocked by any debris as it reads the intensity of the sun and influences temperature control of the HVAC system.
"Duckbill" Old Drain and Duckbill Drain Tube Model T680/T880 Sunload Sensor
8. The A/C clutch will lock out when over/under pressure. To unlock the clutch, cycle ignition key twice or reset it using ESA tool. 9. If the compressor is cycling four times per minute and the ambient temperature is hot, then check refrigerant levels in the system.
Troubleshooting Tips The HVAC system design in the T680/T880 is far different from any other Kenworth model. This system uses the C-CAN data bus to communicate with the CECU. The HVAC Control head has software and may need occasional software updates via ESA. Also, new sensors have been introduced: A/C Compressor Outlet Pressure Sensor, Evaporator Temperature Sensor, Cabin Air Temperature Sensor and the Sunload Sensor. To help troubleshoot, ESA can read HVAC Diagnostic Trouble Codes (DTC’s) and monitor some of the new HVAC sensors. The Service Manual for the HVAC system for the T680/T880, KM811250, can be found in Kenworth ServiceNet under Service\Class8\HVAC. This manual has been revised since the launch of the T680/T880 models and may soon include some of the early/ common issues noted below.
Evaporator Drain The original drain that connects to the HVAC module on the passenger/engine side of the firewall tended not to let the water condensing on the evaporator drain out. Typically the customer would arrive complaining about a wet passenger floor. The end of this tube is called a “duckbill“. If you see the tube 6 | Professional Service Workbook | Volume 110, 4/2014
Cut the tube at angle.
still has the “duckbill“, please cut the tube (shown). Current production trucks have a new drain tube as shown. Please fix this issue on any T680/T880 truck that ends up in your bay for ANY reason. An old drain tube may cause water to fill the HVAC module. Eventually the water will come out of the Heater Core cover and get the passenger side of the floor wet. Cut this tube at angle. The new production drain tube looks similar to the rework shown.
New Drain Tube
T680/T880 HVAC R134A Charge Label
Sleeper Heater Coolant Leak
The charge label is located on the Receiver/ Dryer. If the Receiver/ Dryer was replaced by a previous service the A/C Charge label may not be present. To service a T680/T880 without a label follow the ECAT search process (later in this workbook) explaining how to locate the A/C charge note to see how much R-134a is needed to charge into the A/C system.
A common problem has been reported by some dealerships about coolant in the sleeper bunk area. This may likely be coming from the sleeper module. Inside the module you will find heater tubes (inlet, outlet) that connect the coolant lines under the sleeper to the heater core. These heater tubes may be leaking past the O-rings that are used to seal the connection to the heater core. The original O-rings may dry out and cause this leak. Another cause for the leak has been misrouted coolant lines under the sleeper putting too much pressure on the heater tubes.
Current Charge Labels are as follows; however, T680 (without sleeper) Receiver/Dryer please verify via ECAT with charge label. the charge required for the truck you are working on if the label is missing. T680/T880 with Sleeper: 3 LBS 14 OZ T680/T880 without Sleeper: 3 LBS 4 OZ
Cab TXV Replacement or Evaporator Core Removal To replace or remove the Cab or Sleeper TXV valve you will need to break free a threadlocked nut on the firewall side. Apply counter torque using a large wrench to the TXV valve when doing so. If you don’t, you may bend the tubes going to the evaporator core assembly. This will damage the evaporator core. Even if you try to undo the damage, the O-rings may not seal as intended.
ECAT does not list a part for the O-Rings. Unless otherwise documented, (such as a TIB) engineering has suggested replacement O-Ring P/N: EPDM O-Ring EL701001.
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T680/T880 HVAC Driver’s Thermometer Reading Because the T680/T880 HVAC system monitors cabin temperature, when the driver selects 60°F, the system will try to cool the cab to 60°F. When the cabin temps have reached 60°F the system automatically moves the blend door to prevent the cabin from cooling below 60°F. Then the driver’s thermometer in the duct will indicate less cold is coming out. The same effect works in reverse. When the driver selects 84°F, the system will heat the cab to 84°F. When the cabin temps have reached 84°F, the system moves the blend door so the driver’s thermometer will register a cooler temperature indicating less heat is coming out. THIS IS NORMAL!
Engine Fan Control You may be confused by the lack of an A/C Engine Fan Pressure switch on the T680/T880 HVAC system. There is a single pressure sensor measuring only high side pressure. On the MX engines this is located very near to the A/C Compressor. The A/C Compressor Outlet Pressure Sensor is connected directly to the HVAC Control Head unit in the dash. And since the HVAC Control Head is connected to a J1939 Data Bus (C-CAN), it will tell the Cab Electronic Control Unit (CECU) when it wants the engine fan to turn on. The CECU will then talk to the Engine on the V-CAN J1939 data bus to turn on the Engine Fan.
Some technicians have found their HVAC issue was with a Cummin’s engine parameter. The parameter to allow Engine Fan control via J1939 had been disabled! Check this using Cummins Insite. NOTE: MX engines do not need a parameter to enable engine fan control via the J1939 Data Bus.
Checking the Filters Cab HVAC The fresh air intake module can receive two filters: 1. A standard air filter (X1987001). This filter should always be present. 2. An optional micro particulate or ember filter. – The micro particulate air filter is suggested for those customers in dusty environments. (F37-1018). – The ember filter is for those in hazardous environments such as fire or forestry. (F37-1016). The recirculated air supply has a mesh air filter located behind the dash (W2084001). This filter should always be present.
Sleeper HVAC unit filter has the same part number as the cab HVAC fresh air supply filter (X1987001). This filter should always be present. NOTE: Part numbers are current but always check Web ECAT for latest part numbers!
A/C Compressor Outlet Pressure Sensor
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Standard Air Filter: X1987001
Particulate: F37-1018 OR Ember: F37-1016
Fresh Air Intake Module with Standard Air Filter and Optional Filter
Recirculation Filter Replacement This filter is hidden. The Service Manual contains steps to help you replace this filter, but neglects to tell you to use a mirror to check how much loose material is on the filter before pulling it out. Shine a spot light on the old filter using a mirror, and remove as much of the loose material as possible by hand or shop air. If you do not, the retaining straps will scrape it off and allow the material to fall into the HVAC housing.The only way to clean that is by removing the HVAC Fan motor and vacuuming out the material. You will be doing your customer a favor by cleaning as much off the old filter as possible before removing it.
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T680/T880 HVAC Electrical Troubleshooting Tips P94-1935 is the current electrical system diagram for the T680/T880 HVAC system. Once again, check ECAT for the latest drawing. There has been some confusion on the location of the fuses noted on that diagram and in the service manual. Use the Engine Side and Cab Side Fuse Box charts to convert the P94-1935 Diagram label for the fuse, to the grid location where it is actually located.
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Engine Side Fuse Box Diagram
30 amp J-Case fuse
HVAC BLDC Motor
T680/T880 HVAC Cab Side Fuse Box Diagram Fuse ID
30 amp J-Case fuse
Sleeper PDC 1
HVAC Head Accessory
The fuse and relay located in the sleeper power distribution center are correct and easy to find. They contain the Sleeper HVAC Control Power 5 amp fuse and the A/C Override relay.
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T680/T880 HVAC New ESA HVAC Troubleshooting
HVAC Actuator Test
ESA has some new tools available for T680/T880 models to troubleshoot the HVAC system.
The first tool is the HVAC Actuator Test. This test will check all five actuators and report any faults or issues.
Using ESA you can check for HVAC system Diagnostic Trouble Codes (DTC) in the Diagnose Mode of ESA and then clicking on the HVAC tab. ESA is the only tool needed to clear these codes after the repair is completed. The service manual’s troubleshooting section (KM811250) will have the procedure for any DTC’s detected.
This is accessible in the Monitor Mode of ESA, clicking on the HVAC Box as noted in the screen shot below.
Some HVAC Diagnostic Trouble Codes DTC #
Low Refrigerant Charge
Cab Pressure Sensor Supply Voltage
Compressor Clutch Relay Circuit
Panel Mode Actuator
Defrost Mode Actuator
Floor Mode Actuator
Cab HVAC Blower Motor Speed Adjustment
Battery Potential Power Input
A/C Evaporator Temperature
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This feature has been available since the launch of the T680 model. When selected and run, the HVAC Control Head rotates each of the five actuators fully clockwise and then counter-clockwise several times. This is a pass/ fail test, and if failed, in addition to telling you which actuator, it also sets the appropriate fault code (DTC) as noted above. To date, the most commonly failed actuator in the test has been the Temperature Door, the failure is in the door, with the splines being stripped. Unfortunately, this typically requires a new HVAC module to be installed.
T680/T880 HVAC HVAC Sensor/Control Knob View The second tool is also in the Monitor Mode of ESA. Expanding the CECU3 tree and clicking the HVAC Box allows you to monitor the parameters in the figure below. These are: AC Compressor Outlet Pressure – pressure the HVAC control head is seeing from the sensor. Fan Percent On – at what percent the HVAC control head is telling the fan to run. Requested Fan Speed – the position of the fan knob.
However, these features are not available on all T680/ T880’s. If your truck has older software, you will not see an HVAC selection under the CECU3 menu tree. To enable this tool on trucks with older software you will have to flash the latest HVAC and CECU software. NOTE: Some T680/T880’s when flashed with new CECU software may require a mandatory software update for the Cluster, too. The most useful feature in verifying the A/C Compressor Outlet Pressure sensor is reading a reasonable value.
Temperature Knob Percent Open - the position of the temperature knob.
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T680/T880 HVAC General Servicing Procedures So far, we’ve covered specific issues concerning the servicing of the HVAC system for the T680/T880. The remainder of the workbook reviews general procedures for servicing the HVAC system in any Kenworth truck.
Correct Hose Routing and Clamping Properly Securing Hoses Wrong
Safety Considerations Air conditioning is a pressurized and potentially toxic system. So practice work habits that are safe and protect you and your customer’s truck: • Always wear eye protection because an air conditioning system and bottles of refrigerant are pressurized. • Wear gloves because refrigerants can cause freeze burns. Wear impervious gloves when handling polyglycol and ester lubricants. If they contact skin, wash thoroughly with soap and water. Skin irritation may occur with repeated or prolonged contact. • Don’t work with refrigerants in an unventilated space. Breathing refrigerant will irritate your eyes, nose, and throat. Inhaled in great quantities, it will cause heart irregularities. • Don’t use compressed air to leak-test an R-134a system. At high pressures, a mix of R-134a and oxygen will burn fast enough to cause an explosion! Not only that, shop air is always contaminated with oils and moisture. • R-134a lubricants will damage paint, plastic parts, engine drive belts, and coolant hoses. • Never store any refrigerant in direct sunlight or in temperatures over 125°F, which can raise the gas pressure to the exploding point.
Ample Bend Radius Wrong
Ample Free Length Wrong
Hose Installation Correct installation, clamping, and routing can prevent damage from these causes: • • •
Abrasion against other components wears through the outer cover, damages the internal nylon reinforcement, and causes leaks. Heat sources can deteriorate the hose compound. Prolonged exposure can stiffen or crack hoses. Tight bends at sharp angles can strain fittings and kink or collapse the hose, blocking refrigerant flow.
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T680/T880 HVAC • • • •
Crushing significantly restricts flow, causing hose failure and poor system performance. Cuts on the nylon tube barrier can allow refrigerant leakage. Stretching strains fittings and casing. Ample free length accommodates flexing caused by component movement or fluid flow. Twisting hose assemblies during installation weakens the casing and can loosen fittings under pressure.
Recovering Refrigerant Preparing the Equipment WARNING: Some recovery stations will automatically shut off when the recovery tank is full, but others don’t. Overfilling a recovery tank is dangerous because of the risk of explosion and venting refrigerant into the air. •
• • • • •
Check recovery tank weight to assure it will accept 5 pounds of R-134a. Otherwise, the station may shut off in the middle of recovery because the tank is full. Assure the fittings are clean. The R-134a expansion valve orifice is extremely small and even tiny amounts of dirt or grease will clog it, stopping cooling. Evacuate recovery hoses to remove air that will contaminate the refrigerant. To measure the oil recovered, start with an empty bottle. – Close the oil injector valve. – Drain any oil still in the station.
Recovering the R-134a • • • • •
Open the station’s manifold valves, tank valves and service hose valve, if so equipped. Start recovery. It should take less than five minutes. When recovery has completed its cycle: – Watch the low side gauge for three minutes. – If the gauge rises above zero, R-134a remains in the system. Repeat the recovery cycle.
Shut the manifold valves. Measure the amount of oil recovered. – Open the oil valve. – Drain oil into the measurement bottle. – Replace this amount of oil before you recharge the system. – Properly dispose of the recovered oil. – Never re-use oil. It is contaminated.
Remove the high and low side hoses. Begin repairs and replacements.
Close the station’s manifold valves to prevent the escape of refrigerant. Connect the station service hoses to the high and low sides of the system.
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T680/T880 HVAC A/C Refrigerant Oil Replacement – Oil Balancing Under normal operating conditions oil is circulated through the A/C system with the refrigerant. When the system is not operating, the oil settles to the lowest points in the system. These low points are typically the suction lines and evaporator. Oil will typically settle out in the cooler parts of the system. When a component is serviced the small amount of oil that is retained in each of the components requires replacement. It is necessary to balance the oil charge in the vehicle when servicing components and/or the refrigerant charge. The chart below identifies the component, the amount of PAG (polyalkylene glycol oil used in R-134a) oil to be added to the system, and the method of adding the oil that is recommended.
Amount of SP15 oil to add
Condenser Receiver Drier
Add to evaporator inlet tube or inject to low side port during A/C charge Add to condenser inlet tube or inject to low side port during A/C charge
1.5 oz/45ml Add to receiver drier inlet or inject to low side port during A/C charge
Large leak (cut A/C line)
Small leak (loose fitting)
Suction line to rear evaporator
Other line or hose
Method to add
Balancing procedure – see compressor replacement section
When replacing a component in the A/C system it is important to replace the PAG SP15 oil that is lost with the component and any oil lost that may have escaped from the system. The total amount of oil in the system is listed on the sticker of the compressor and is 10.1 oz (300 cc). It is important for proper compressor lubrication that this amount be maintained as close as possible to the design intent.
Oil Balancing Procedure – Example 1 A truck that requires new compressor, new condenser, and refrigerant charge. System has been flushed. Existing Compressor Areas
Drain oil from old compressor
Oil remaining in old compressor (0.5 oz will remain in compressors as film coating)
Condenser replacement oil (from oil charge chart)
Oil in recovery machine
Amount of oil to be replaced
5.5 oz total
New Compressor Areas
Shipped with system oil amount per design intent
Amount of oil to be replaced. Subtract this from the new compressor oil amount
- 5.5 oz
Amount of oil that needs to be drained from new compressor
Oil Balancing Procedure – Example 2 Inject to low side port during A/C charge
Add to compressor – see balancing procedure
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A truck that requires new condenser and refrigerant charge only. Areas
Condenser replacement oil (from oil charge chart)
Oil in recovery machine
Amount of oil to be replaced
3.0 oz total
T680/T880 HVAC Evacuation Procedures Evacuation removes as much air and water as possible before recharging. • Air displaces R-134a, lowering its performance. • R-134a and compressed air form a potentially explosive mixture. • Water forms an acid when mixed with refrigerant and oil. • Water forms ice crystals that plug the expansion valve. • Water saturates and deteriorates the desiccant, contaminating the system with desiccant particles. Evacuation produces a deep vacuum to vaporize water out of the thick oil. Then time is needed to pull the water out of the system, including such distant components as the sleeper evaporator.
Effect of Shop Temperature As shop temperature rises, less vacuum is needed to vaporize water. Service departments at higher altitudes must adjust vacuum to compensate for lower atmospheric pressure.
9. Continue pumping: a. If evacuating without a thermistor, continue to pump for at least 45 minutes – the longer the better, for up to 12 hours. b. If evacuating with a thermistor, pump until the thermistor reads below 1000 microns for at least 5 minutes. 10. Close the station valves to the vacuum pump and watch the thermistor gauge. a. Any remaining vaporized water will cause the gauge to slowly rise and then stabilize, signaling the need to pump longer to remove all moisture. b. If the thermistor gauge continues to rise without stabilizing, there is a leak in the system. c. If the thermistor reading remains steady, the system is evacuated. 11. When the system is evacuated, immediately charge the system.
Vacuum Needed to To evacuate the system: Boil Water at Shop 1. Turn the engine OFF. Temperatures 2. Turn the A/C VACUUM system ON. (°F) (Inches) Hg* 3. Attach the high 120 26.45 and low side 110 27.32 service hoses. 100 27.99 4. Open the 90 28.50 manifold valves. 80 28.89 5. Determine 70 29.18 the vacuum needed (table). 60 29.40 6. Pump the system 50 29.66 down for about 15 40 29.71 minutes, or until the 30 29.76 low side gauge reads 20 29.82 below 25“ Hg. 10 29.86 7. Close the station *Subtract 1" for every 1000' above sea level. valves to the vacuum pump. 8. Check for leaks: If the low side gauge rises back toward zero more than 1“ Hg in a minute, the system is leaking. Volume 110, 4/2014 | Professional Service Workbook | 17
T680/T880 HVAC Charging CAUTION: R-134a systems are charged by weight. You cannot “top off“ an R-134a system using the sight glass. Overcharging will cause the system to perform poorly. 1. Find A/C Refrigerant Charge Label. T680/T880 is on Receiver/Dryer. If the Receiver/Dryer has been replaced, it may be missing. T440, T470, T660, T800, W900, C500 is on the engine side of the HVAC assembly – right behind the Receiver/Dryer.
If you cannot locate the charge label, for example the T680/T880 Receiver/Dryer has been replaced, look up charge label in Web ECAT using this process: In Web ECAT enter the search phrase “refrig.“ An item will be located named A/C REFRIGERANT DECAL. Open that item and the A/C Refrigerant charge will be noted. Open the subject line by clicking on the [+]. The screen shot below has already been opened.
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T680/T880 HVAC 2. Turn the engine OFF. 3. Turn the A/C system ON. 4. Either: a. Fill the charging station with the correct weight of R-134a. b. Enter the correct weight at the station control panel.
Checking Coolant Levels for the T680/T880 Avoid Misdiagnosis
5. If necessary, heat the R-134a. 6. Close the low side manifold valve. 7. Begin charging by pushing the charging button or turn the charging valve.
Coolant levels MUST be checked with the vehicle on level ground. If parked on an incline, the unique shape of the T680/T880 coolant expansion tank may cause inaccurate readings which may lead to the tank being overfilled. (If the cooling system has been recently drained, follow the purging procedure in the operator’s manual to ensure all air has been properly bled from the system.)
CAUTION: As the station charges through the high side hose, if the low side gauge does not slowly rise, the system is blocked.
To avoid being surprised by low coolant levels, periodic checks of the coolant level should become a regular part of the customer’s daily routine. If they are familiar with what is “normal,” they will notice immediately if something has changed (TIB 42-052).
8. Close the high side manifold valve. WARNING: Never run the truck engine with the charging station high side manifold valve open. The truck’s compressor may pressurize the charging station tank, causing an explosion. 9. Remove the high side hose from the truck service port. 10. Start the truck engine and let it idle at 1500 rpm. 11. Open the low side manifold valve. 12. Allow the compressor to draw any remaining R-134a out of the hoses. 13. The truck is now fully charged. 14. Remove the low side hose. 15. Test the system for proper performance.
Coolant level with vehicle on flat ground
Coolant level with vehicle on 10° slope
The minimum fluid level is determined by the line on the surge tank indicated by the letters “MIN”. This indicator is located below the fill cap. Do not add coolant to the surge tank unless the coolant level does not rise to the “MIN” line regardless if the system is hot or cold.
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T680/T880 HVAC WARNING: Never open the surge tank when the engine is hot. Removing the fill cap on a hot engine can cause scalding coolant to spray out and burn you badly. If the engine has been in operation within the previous 30 minutes, be very careful in removing the fill cap. Protect face, hands, and arms against escaping fluid and steam by covering the cap with a large, thick rag. Do not try to remove it until the surge tank cools down or if you see any steam or coolant escaping. In any situation, remove the cap very slowly and carefully. Be ready to back off if any steam or coolant begins to escape. 4. Top off the cooling system when coolant does not rise to the level indicated as ‘MIN’ on the surge tank. The surge tank is translucent which allows visibility to the coolant level. Add coolant through the surge tank fill cap. Do not remove the pressure cap to fill the cooling system. When adding coolant to the system, be accurate. If overfilled, the tank may overflow with the engine running as the coolant heats and expands. The excess coolant is then blown back onto the front of the engine by wind-speed and the radiator fan. This condition has often been misdiagnosed as a leaking water pump. Technicians notice low coolant levels in the surge tank and drops of coolant near the weep hole on the water pump. Avoid this mistake by being absolutely sure that the coolant tank has NOT been recently topped off or shows signs of overflowing. If records indicate that coolant has been recently added, don’t immediately assume the coolant pump is leaking.
Refilling the Radiator If the cooling system is built with drain valves in the upper engine coolant pipe, open them before filling the surge tank. Close any open coolant drains in the system. 1. Remove the surge tank fill cap (Do not remove the surge tank pressure cap). 2. Fill the system with premixed coolant through the surge tank fill cap. Pour coolant at a steady flow rate until the surge tank is full (to the base of the fill neck). It may be necessary to pause for one minute and then re-fill if the fluid level has dropped. 3. Close any drain valves that were opened before filling. 20 | Professional Service Workbook | Volume 110, 4/2014
Pressure Cap (Never to be removed)
Fill Cap (Service point)
4. Start the engine and idle at low RPM. 5. During low RPM idle, air will purge from the cooling system which will lower the coolant level in the surge tank. Continue to fill the surge tank until the coolant level remains approximately ½-inch above the “MIN” line. This may take up to two minutes, depending on the outside temperature. 6. Operate the engine throttle until the operating temperature stabilizes (when the thermostat opens). 7. Fill the surge tank as necessary to raise the coolant level to ½-inch above the “MIN” level. 8. Operate the engine at high idle for another 10 minutes and then fill the surge tank again to ½-inch above the “MIN” level. 9. Replace the surge tank fill cap. Check the coolant level after each trip. Add coolant as necessary. You may find the coolant level is not up to the correct level soon after you have filled the radiator. This may be because all of the trapped air in the system has not yet been purged. It takes a little time for all the air to leave the system after you fill the radiator.
Coolant Pump Leakage The large number of unnecessary coolant pump replacements in the field (TIB 42-052). All chassis equipped with the MX-13 engine built during model years 2013 and 2014 are affected. Trucks are brought to the dealership with low coolant fault codes. The technicians inspect the surge tanks to ensure the engines have enough coolant. If coolant is missing, they check for leaks and, most of the time, they find coolant drips at the “weep hole” of the
T680/T880 HVAC Weep-Hole Leak Classifications Classification I Wetness or discoloration
Do not replace
(weep hole refers to the opening in the housing below the shaft). During hard driving cycles, excessive engine vibrations can increase and disturb the fluid film, increasing the chance of a small leak. This is also a normal pump behavior. PACCAR MX-13 water pump service recommends inspecting the front of the coolant pump housing, illuminating the area with a spot or portable light. If a leak at the pump shaft seal is discovered, the severity must be classified in order to determine if the coolant pump requires replacement.
T680/T880 HVAC Key Points
Do not replace
The HVAC system installed in the T680/T880 operates differently from the systems in other Kenworth Model groups.
Drivers who are used to the HVAC systems in Kenworth’s other models may complain the T680/T880 HVAC system is not working properly.
Continual dripping Replace
coolant pump. This is often the cause of a false R&R of the pump Investigations from the division have shown that the “Surge Tank” design is the main root cause for the “Low” coolant fault codes. With RC7 the fault code should be deactivated, but will still remain in the DAVIE Log. The replaced, suspect-pumps are send back to Concentric UK for inspection and bench tests. Most of the pumps pass the test and are marked as “NTF" or “No Trouble Found.” The coolant pump’s mechanical seal uses engine coolant as fluid film for proper operation. This fluid film creates a controlled leak path that, over time, will reflect at the weep hole as a dry red coolant spot. This red spot at the weep hole is normal
Common Complaints or Issues
Driver’s duct thermometer reading issue – System will not cool below 60°F or heat above 84°F. • Wet passenger floor – Check evaporator drain for “duckbill” and replace. • Missing charge label – Locate A/C charge note to see how much R134A is needed to charge system. • Coolant in sleeper bunk area – Replace EPDM O-ring. • No A/C Engine Fan Pressure Switch – Locate A/C Compressor Outlet Pressure sensor connected to HVAC Control Head unit in dash. • Disabled Cummins engine parameter – Check Cummins Insite. Distinguish between a valid complaint and a misunderstanding of how the system works before servicing the system. •
If you would like to attend a comprehensive, hands-on course on the new HVAC systems, please sign up for Course 304 (HVAC) at the Kenworth Dealer Training website.
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Test Your Knowledge Instructions: Follow the steps on the Answer Sheet on the next page to take your test online, to fax, or to mail your test.
1. The HVAC system installed in the T680/T880 models has advanced features compared to other Kenworth model groups. a. True b. False 2. In what component of the air conditioning system does R-134a refrigerant easily absorb heat? a. Condenser b. Evaporator c. Receiver/Dryer 3. Which component of the air conditioning system is like a radiator for the refrigerant? a. Condenser b. Evaporator c. Receiver/Dryer 4. The new dash control unit communicates on a new J1939 data bus exclusive to the T680/T880’s C-CAN. a. True b. False 5. How many different fan control speeds can be selected with the Fan Control Dial in the cab unit? a. Four b. Six c. Eight
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6. To help troubleshoot the HVAC system in the T680/T880, ESA can read Diagnostic Trouble Codes (DTC’s) and monitor some of the new HVAC sensors. a. True b. False 7. Where can you find information on how much R-134a is needed to charge into the A/C system on a T680/T880 truck? a. On the charge label located on the Receiver/Dryer.
b. On the A/C charge note located via ECAT search if the label is missing.
c. Both methods can provide the same information.
8. Which of the following components is used to turn on the engine fan in the T680/T880 HVAC system? a. The A/C Compressor Outlet Pressure sensor
b. The A/C Engine Fan Pressure switch
c. Either component can be used
9. Which type of Cab HVAC filter is suggested for customers in dusty environments? a. The ember filter
b. The micro particulate air filter
c. A standard air filter
10. Which of the following are new ESA HVAC troubleshooting tools? a. HVAC Actuator Test
b. HVAC Sensor/Control Knob View
c. Both of the above
Answer Sheet Faster, Easier Testing ONLINE! Take your Professional Service test and get your score instantly, ONLINE! Here’s how: 1. Go to the Kenworth Training page and access the training website in one of two ways: a. From the Internet, type www.kenworth-training.com into the browser address box. Click “Go”. Enter your password to display the Kenworth Dashboard – OR b. From the Kenworth DealerNet Home Page:
1) Click on the “Training” tab at the top of the page. 2) Select “Service” from the menu on the left. 3) Select “Service Training”. 4) Verify that the displayed log-in information is correct, then click the “Submit” button. 2. Click on “Truck Service” at the top of the page. 3. Click on the box titled “Workbooks and Update Tests”. 4. Moving the cursor reveals workbook or Update tests you may want to take.
It’s fast and easy, and you’ll see your score instantly!
Good luck! If you’re faxing or mailing your test, please print your name and dealership information below. Name: PRINT ONE LETTER IN EACH BOX. LEAVE A BLANK BETWEEN NAMES AND INITIALS.
Mark the box for the correct answer to each test item on previous page. Then fold and mail this Answer Sheet to the address on the back, or fax to the Kenworth Professional Service Coordinator at Burgio, Cooney and Associates
Fax: (816) 353-4206
T680/T880 HVAC System 1. a b c d
4. a b c d
8. a b c d
2. a b c d
5. a b c d
9. a b c d
3. a b c d
6. a b c d
10. a b c d
7. a b c d Volume 110, 4/2014 | Professional Service Workbook | 23
Take Your Test Online Go to www.kenworth-training.com
1. Click on the “TRUCK service” tab. 2. Click on the “Professional Service” icon.
3. Click on the Workbook Test or Update Test button to take the online tests. When you are finished taking the test click the submit button at the bottom of the page. Click on the Workbook icon to open the Workbook. Click the Newsletter button to open the Newsletter. Once opened you can save or print.
All About PTOs
All About PTOs
FOLD AND TAPE
PROFESSIONAL SERVICE WORKBOOK Burgio, Cooney + Associates 13665 e 42nd terrace s – suite d independence, mo 64055-7343