APU TROUBLESHOOT TREE

Transcription

1 APU TROUBLESHOOT TREE Abbreviations & Definitions APU-Auxiliary Power Unit VOM-Volt Ohm Meter FCR - Fan, Condenser, Radiator assembly HVAC - Heating, Ventilating, and Air Conditioning Alt - Alternator Comp - Compressor REV IR Instructional Symbols & Meanings Volt Ohlms Meter - Use a VOM meter to read the electrical current in wires, some engine components, the APU', and sub components. Test Light - A test light can substitute a VOM in cases where an exact electrical reading is not necessary. Physical Check - The described instructions may require a physical check. A physical check involves touching a component by hand. Audible Check - This symbol signifies the need to listen to a component or sub component to recognize symptoms or failure types. Safety Symbols & Meanings Pinch/Entanglement Hazard - Described component has hazardous revolving, running, spinning, or similar action, including pinch and sheer points, which can cause physical injury. Shock Hazard - Described component has hazardous electrical currents, which can cause physical injury. Burn Hazard - Described components and/or related materials are extremely hot and can cause physical injury when touched. Visual Check - This symbol requires that you visual inspect the described unit or sub unit to recognize symptoms or failure types.

2 Engine Will t Start Does engine turn over? Does unit have power? Are controllers lit or appear to have any power? Does Fuel Solenoid Engage when engine turns over? a. Starter fuse is blown b. Orange wire plug on starter is disconnected a.blown fuses and/or relays b. Fuel Solenoid bad a. Unit is getting insufficient fuel, has air in fuel lines due to low fuel level in truck, has loose fuel block fittings, pick-up tube too short, or loose or damaged fittings and hoses causing a leak b. Bad fuel manager or dirty fuel filter. a. 200 amp fuse in battery box blown b. batteries in thermostat control need change c. Fuse or relay in either fuse boxes may be blown d. wires may have disconnected from control e. if thermostat recently serviced, make sure the small red diode is still located in the post located in the back of the thermostat. Engine Runs & Shuts Down Does unit bogg down? Does unit shut down immediately? Speed sensor may need to be cleaned, adjusted, and/or replaced. Does DSE control show low RPM code? a. Check fuel solenoid, fuses, wires, relays, all connections. & Unit may not be getting insufficient fuel a. Check if unit will prime by pushing down on the pump located on the fuel manager b. check fuel lines & filter c. check fuel block & fittings d. fuel pick up tube may be too short causing it to suck in air when fuel is low or pick up tube is too long causing it to pull diesel fuel residue into the system and causing blockage. a. check/change air filter

3 Unit is Overheating Is unit overheating in hot weather? Is the radiator tube valve or thermostat housing valve open? Is coolant level in truck low? Add coolant and check lines & for any leaks. Open valve(s) to circulate coolant flow to reduce temperature. Temperature sensor may be bad and will need replacement. Is unit overheating in cold weather? Is coolant level in truck low? Add coolant and check lines & for any leaks. Temperature sensor may be bad and should be replaced.

4 Unit Does t Cool (Closed Loop) te: Unit must go to high idle for the following to work. If there is an electronic snap valve for your AC/Heat manex, make sure it is closing fully. A loose or broken AC compressor belt will also cause AC failure. Does throttle solenoid pull back? Check if fuse is blown & change. Fuse Good. Does solenoid get power when AC is on, and is the freon charge good? te: Power comes to the throttle solenoid from the AC pressure switch, if the throttle solenoid is not pulling back while the freon is good, then the solenoid is bad. Always check the freon charge.an incorrectly installed throttle solenoid will burn up quickly. Solenoid is bad. Warning: When installing a new solenoid, the solenoid must be set properly or it will burn up quickly & need to be replaced again. Freon Charge good.. Freon Charge bad. If high, reduce by 1/2 lbs & check again later. Check low side for erratic charge, if charge is erratic, replace expansion valve. Fan is not running. Fan fuse may be blown. Wires may be loose or connections are bad. Does thermostat have power? Is thermostat on cool mode? Is fan on Auto? Switch fan to ON and test AC again. Change thermostat batteries Set thermostat to 'Cool' mode. Does t Work. a. pressure switch may be bad b. Freon charge low Does t Work.

5 Does fan switch have lights to indicate power? Does thermostat have power? Set fan to 'On' mode and test by adjust temp. Does t Work. Is fuse on compressor clutch okay? Change thermostat batteries. Does t Work. Fuse and/or electrical issues. Make sure pressure switch wires are connected Does t Work. Test pressure switch wires by touching them together. If clutch comes on, pressure switch is bad. Evaporator Freezes AC compressor runs after removing one lead wire? Is temp probe located on 2nd bottom row & 2" from left? a. check AC switch wires for power b. Adjust freon level c. If Freon charge is erratic, the expansion valve is bad. Relocate probe accordingly. a. Does AC switch wires have power? Is freon level high? Freon Level High, reduce by 1/2 lbs and check again later Check fuses and look for loose connections check low side to see if freon charge is erratic. If freon charge is erratic, replace the expansion valve.

6 Integrated AC System Failure AC does not work. If the truck batteries have a low charge, it may shut off your unit's AC system. Run your truck for a few minutes prior to starting the APU, and then run the AC again. Turn truck key to accessory to start APU & run AC. Is truck AC system runing cool? You may have a Freon leak. Is Condenser Fan running? Wire bad or connection bad. Change wire and test ECU & connection. Does AC compressor kick on? Test AC in line fuse and check the compressor wire from ECU for bad connection. ECU has no power. Pink wire from ECU to APU have power? a. Check the inline Fuses b. Check the solenoid fan switch Replace wire and test again. a. Test light the fan solenoid and all wires b. Check wires in APU belly pan for corrosion or disconnection. a. 40AMP truck & APU compressor fuses are blown b. bad relay in ECU c. deustch plug connections bad ECU has no power.

7 Unit Will t Heat AC Only Evaporator Make sure all valves on truck are open, except Radiator valve stays closed for added heat Make sure truck blowers are working properly. te: Key must be at the 'on' position for unit to run. This system will not maintain normal heat when outside temperatures fall below 20 degrees. Coolant hoses may need correction. Call WPS. Electronic Snap Valve Does Elect Snap valve (tested) open (clicks when opnes)? a. Ensure switch next to blower knob is on 'Heat' b. Ensure thermostat control is on heat mode AC & Heat Evaporator Manual valves must be open for coolant flow into evaporator. Check Fuse & Wiring Alternator t Charging Is alternator belt loose or broken? Does truck batteries pass load test? a. APU battery cables may have faulty connections or corrosion b. alternator wires may be bad or alternator is bad. Call WPS. Run truck engine for a few minutes to charge batteries. Turn truck key to accessories and run APU. Replace Belt

8 Wire Harness Failure - Premium APU Visually check and replace 200 AMP fuse if needed. Check for bad fuses in fuse box & replace. 10 ga solenoid wire on starter has power? Check for loose connections or replace wire. Wires are good. Check APU battery cables for any bad/loose connections. Check ground wire with VOM. Under 12V is bad wire. Replace bad wire. Wire is good. Check relays and fuses by swapping & replacing. Replaced relays & tested good. Still no power. Check orange wire in DSE for bad connection Connection is fine. a. DSE control not working. b. alt wire &/or connection loose or corroded Call WPS. Replace bad relays and fuses.