Fault Finding On The Air-Conditioning System Following Complaints About Cooling Output
Information
The following fault finding table should be used if the cooling output is not OK. The Function test on air conditioning must be carried out beforehand using the PIWIS Tester.
> 870101 FUNCTION TEST ON AIR CONDITIONING
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.
The sequence of the test steps does not necessarily have to be followed and is merely intended as a means of performing fault finding.
| Condition | Specification OK | Specification not OK |
|---|---|---|
| 1)
Check cooling output Establish operational readiness/switch on ignition and carry out a function test on the air-conditioning system using the PIWIS Tester. > 870101 FUNCTION TEST ON AIR CONDITIONING |
Function test was successful, but the cooling output is still too low Continue with Step 2) . |
Repair components indicated in the fault memory. |
| 2)
Check refrigerant pressure. Connect air conditioning service equipment to the vehicle, read out measured values from pressure sensors (PT1, PT2 and PT3) using the PIWIS Tester (Thermal management control unit \ Actual values/input signals \ Refrigerant circuit sensors) and compare them with values from the air conditioning service equipment. Observe the tolerance values of the respective air conditioning service equipment. |
Refrigerant pressure OK. Continue with Step 3) |
If a pressure sensor deviates by > 2 bar, replace pressure sensor. > 878319 REMOVING AND INSTALLING PRESSURE SENSOR (PT1) > 878319 REMOVING AND INSTALLING PRESSURE SENSOR (PT2) > 878319 REMOVING AND INSTALLING PRESSURE SENSOR (PT3) |
| 3)
Check refrigerant quantity. Extract refrigerant using air conditioning service equipment. > 870317 DRAINING AND FILLING REFRIGERANT R134A > 870317 DRAINING AND FILLING REFRIGERANT R1234YF |
Refrigerant quantity OK. Continue with Step 4) . |
Due to the low refrigerant quantity, evaluate whether there is a leak and/or if refrigerant needs to be added. Look for the leak and fix it (see Information). 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. Fill the repaired or leak-tight air-conditioning system with the correct amount of refrigerant. > 8X00IN TECHNICAL DATA FOR AIR-CONDITIONING SYSTEM WITH R134A AND R1234YF |
| 4)
Check outside temperature sensor. Read out the measured value for outside temperature using the PIWIS Tester (Front-end electronics control unit \ Actual values/input signals \ Outside temperature sensor) and compare it with the ambient air thermometer. |
Outside temperature sensor OK. Continue with Step 5) |
Replace outside temperature sensor. > 916819 REMOVING AND INSTALLING OUTSIDE TEMPERATURE SENSOR |
| 5)
Check evaporator temperature sensor. Remove temperature sensor (but leave it plugged in) and let it adjust to the ambient temperature. Read out the value using the PIWIS Tester (Thermal management control unit \ Actual values/input signals \ Refrigerant circuit sensors) and compare it with the value from a temperature gauge. |
Evaporator temperature sensor OK. Continue with Step 6) . |
If the value deviates by > 2 degrees Celsius, replace evaporator temperature sensor > 871319 REMOVING AND INSTALLING EVAPORATOR TEMPERATURE SENSOR |
| 6)
Check air inlet housing. There must be no water going into the heating/fresh-air unit and it must be free of dirt and foreign bodies. |
Air inlet housing OK. Continue with Step 7) . |
Clean or replace air inlet housing. > 851419 REMOVING AND INSTALLING AIR INLET HOUSING |
| 7)
Check particle filter for dirt and dust particles. > 851819 REMOVING AND INSTALLING PARTICLE FILTER |
Particle filter OK. Continue with Step 8) |
Replace particle filter. > 851819 REMOVING AND INSTALLING PARTICLE FILTER |
| 8) Check condenser, condenser fan and cooling-air flaps for dirt, damage and ice. | Condenser, condenser fan and cooling-air flaps OK. Continue with Step 9) |
Clean or replace condenser, condenser fan and cooling-air flaps. > 875019 REMOVING AND INSTALLING CONDENSER > 875319 REMOVING AND INSTALLING CONDENSER FAN > 193519 REMOVING AND INSTALLING COOLING-AIR FLAPS |
| 9)
Check expansion valve (EXV2) for internal soiling and function. Use the PIWIS Tester to move it to its end positions (Thermal management control unit \ Actual values/input signals \ Refrigerant circuit sensors) and compare it with the value from a temperature gauge. |
Expansion valve (EXV2) OK. Continue with Step 10) |
Replace expansion valve (EXV2). > 887019 REMOVING AND INSTALLING EXPANSION VALVE 2 |
| 10)
Check water drain hose on heating/fresh-air unit. It must not be stuck with wax or underbody protection or show signs of dirt or soiling. Condensate must be able to drain away freely. |
Water drain hose OK. Continue with Step 11) |
Clean or replace water drain hose. > 852119 REMOVING AND INSTALLING WATER DRAIN HOSE |
| 11)
Check passenger compartment evaporator. It must be free of ice, dirt, damage and foreign bodies. Check using an endoscope. |
Evaporator OK. Continue with Step 12) |
Replace evaporator housing (evaporator is not available as a spare part). > 851519 REMOVING AND INSTALLING HEATING/FRESH-AIR UNIT |
| 12)
Check refrigerant lines for signs of damage. They must not be crushed, damaged or kinked. |
Refrigerant lines OK. Continue with Step 13) |
Due to the considerable amount of time and effort involved, this measure should only be carried out if the previous measures were not successful. Replace the relevant refrigerant line. |
| 13)
Check ventilation covers in passenger compartment. They must not be stuck with wax or paint or show signs of dirt or soiling. Air must be able to flow out freely. |
Ventilation covers OK. No further action required. |
Due to the considerable amount of time and effort involved, this measure should only be carried out if the previous measures were not successful. Check/clean or replace ventilation cover. > 856519 REMOVING AND INSTALLING VENTILATION COVER |