Fault Finding On The Air Conditioning System Following Complaints About Cooling Output
Information
The troubleshooting steps shown must be used if complaints are received about the cooling output of the air-conditioning system.
Information
Leaking air-conditioning systems must only be filled with nitrogen or forming gas for the purposes of leak testing.
Leak detector additives must only be used if there is no clear indication from the leak test using nitrogen or forming gas.
Leak detector additives from Waeco are compressor oils with fluorescent components and meet the requirements for the operational fluids and fuels.
Only compressor oils with fluorescent components may be used as leak detector additives.
Leak detector additive: Tracer UV additive (500 ml container) TP-3525-500 specifically for Waeco air conditioning service equipment.
Leak detector additive: Tracer UV additive (stick) TP-9825-0301; can be used universally for all air conditioning service equipment.
For vehicles with refrigerant R134a, the leak detector additive Traserline TP 3860 in dissolved form can also be used.
Special adapter kits are required for filling the Tracer UV additive (stick) TP-9825-0301 and Traserline TP 3860; these are also available from air conditioning service equipment providers (e.g. Waeco).
Fluorinated greenhouse gases are not permitted in leak testing.
Instructions for use and the procedure for filling the air-conditioning system can be found in the operating instructions provided by the respective air conditioning service equipment provider.
| Status | Specification OK | Specification not OK |
|---|---|---|
| 1) Check the cooling output, temperature and air flow. Check the air distribution by making adjustments on the air conditioning control panel. Start the vehicle and check the air conditioning system for the prescribed nominal temperature values. > WM, 870101 CHECKING AIR CONDITIONING |
Specified air flow and temperature is reached. Air distribution is working. Next Step 2 . |
Insufficient air flow from the exhaust vents. Next Step 3
. Required temperature is not reached. Next Step 2 . |
| 2) Perform on board diagnostic for all control units > 9900 - PIWIS Tester 3 | No fault memory stored, air flow and temperature complies with specified nominal values. Function OK. No further action required. No fault memory stored and the temperature does not reach the specified nominal values. Continue with Step 4 . |
Fault present: Work through the fault memory in accordance with Guided Fault Finding instructions. Next Step 1 . |
| 3) Check the following points one after the other. Replace if necessary. Remove particle filter and check for dirt and dust particles. WM, 851819 REMOVING AND INSTALLING PARTICLE FILTER Check fan motor for correct operation and control. If any Use wiring diagram. Check the mechanical operation of the servo motors/flaps using > 9900 - PIWIS Tester 3 . |
Fan motor OK. Particle filter OK Servo motors/flaps OK. Next Step 4. |
Replace fan motor. WM, 853019 REMOVING AND INSTALLING HEATER/FRESH-AIR BLOWER MOTOR Replace particle filter. WM, 851819 REMOVING AND INSTALLING PARTICLE FILTER Replace servo motor. Example: > Removing and installing servo motor for defroster If servo motor flap is faulty, replace heating/fresh air unit. WM, 851519 REMOVING AND INSTALLING HEATING/FRESH AIR UNIT Following repairs, continue with Step 1. |
| 4) Connect air conditioning service equipment, measure high and low pressure and compare with nominal values. > 8X00IN NOMINAL VALUES FOR PRESSURES AND TEMPERATURES |
High and low pressure OK. Function OK. No further action required. |
High pressure too high. Continue with Step 5. High pressure too low. Continue with Step 6. Low pressure too high. Continue with Step 7. Low pressure too low. Continue with Step 8. |
| 5) High pressure too high. Check the following points one after the other: Check the condenser for dirt/dust particles and damage. Check electrical function, condenser fan activation. Drain refrigerant and measure and document the amount of refrigerant removed. Too much refrigerant. > 870317 DRAINING AND FILLING REFRIGERANT R134A > 870317 DRAINING AND FILLING REFRIGERANT R1234YF |
Clean condenser. Repair activation mechanism for electric fan. Use wiring diagram. Fill the air conditioning system with the prescribed amount of refrigerant. > WM, 8X00IN TECHNICAL VALUES - AIR CONDITIONING Next Step 1. |
|
| 6) High pressure too low. Check the following points one after the other: Check electrical operation, air-conditioning compressor activation. Drain refrigerant, measure and document the amount of refrigerant. |
If the amount of refrigerant is correct, remove the expansion valve and check for foreign bodies (e.g. chips, abrasion). > 877019 REMOVING AND INSTALLING EXPANSION VALVE > 870317 DRAINING AND FILLING REFRIGERANT R134A > 870317 DRAINING AND FILLING REFRIGERANT R1234YF Replace expansion valve if necessary. Next Step 1 |
Repair air conditioning compressor activation mechanism. Use wiring diagram. If there is not enough refrigerant, fill the air conditioning system according to specifications. > WM, 8X00IN TECHNICAL VALUES - AIR CONDITIONING Check refrigerant circuit and connection points using a leak detector. >> Once you have determined the cause of refrigerant loss, replace gasket or spare part. Next Step 1 |
| 7) Low pressure too high. Check the following points one after the other: Drain refrigerant, measure and document the amount of refrigerant. Too much refrigerant. > 870317 DRAINING AND FILLING REFRIGERANT R134A > 870317 DRAINING AND FILLING REFRIGERANT R1234YF |
If the amount of refrigerant is correct, remove the expansion valve and check for foreign bodies (e.g. chips, abrasion). > 870317 DRAINING AND FILLING REFRIGERANT R134A Replace expansion valve if necessary. Next Step 1 |
If there is too much refrigerant, fill the air conditioning system according to specifications. > WM, 8X00IN TECHNICAL VALUES - AIR CONDITIONING Next Step 1 |
| 8) Low pressure too low. Check the following points one after the other: Drain refrigerant and measure the amount of refrigerant. Not enough refrigerant. > 870317 DRAINING AND FILLING REFRIGERANT R134A > 870317 DRAINING AND FILLING REFRIGERANT R1234YF Disconnect lines on the air-conditioning compressor and check for foreign bodies (e.g. chips, abrasion). > WM, 873419 REMOVING AND INSTALLING AIR CONDITIONING COMPRESSOR |
If the amount of refrigerant is correct, remove the expansion valve and check for foreign bodies (e.g. chips, abrasion). > 877019 REMOVING AND INSTALLING EXPANSION VALVE > 870317 DRAINING AND FILLING REFRIGERANT R1234YF Replace expansion valve if necessary. Next Step 1 |
Fill the air conditioning system with the prescribed amount of refrigerant. > WM, 8X00IN TECHNICAL VALUES - AIR CONDITIONING Check refrigerant circuit and connection points using a leak detector. >> Once you have determined the cause of refrigerant loss, replace gasket or spare part. Replace air-conditioning compressor if necessary. Next Step 1 |