Checking Refrigerating Capacity (Short Test)
Data
Max. difference between coldest and 3 °C
warmest outlet temperatures
(switching off/on time of
refrigerant compressor)
Coldest air outlet temperature 3.0 °C
from center outlet
Conventional tools
2 thermometers -20 °C to +70 °C
Digital temperature measuring instrument with 4 measuring probes
Robbi temp 90020
Air temperature measuring probe 90023
(cable length 4.5 m)
Supplier:
Switzerland: Kent-Moore (Europe) AG
P.O. Box, CH-6340 Baar
Germany: Kalte-Fischer
Postfach 266, Augsburgerstr. 289 - 291
D-7000 Stuttgart 60
Digital temperature measuring instrument with 4 measuring probes
Therm 2263-2
4-point measurement
Changeover switch 2235-4
Air temperature measuring probe W453-5
(cable length 3 m)
Supplier:
Germany: Ahlborn MeB- und Regelungstechnik, EichenfeldstraBe 1 - 3,
D-8150 Holzkirchen
Quick test
Where complaints do not concern the air conditioning system. Testing following minor repairs, lengthy storage or similar.
Test method for room temperatures from +20 °C to +40 °C. Check values can be read after approx. 5 minutes.
Test conditions
1 The vehicle must not be exposed to direct sunlight either before or during the test.
2 Check tension of ribbed V-belt for compressor drive.
3 Check function of auxiliary fan by switching on ignition and shorting the two plugs at the pressure switch (S32).
- In vehicles with small auxiliary fan,
the auxiliary fan and the engine fan should operate.
S25/4 100/110 °C temperature switch
in modules 201.024 (AUS), (J) and
201.028
S25/5 105/115 °C temperature switch
in model 201.034/035
S25/5 105/115 °C temperature switch
in model 201.029
S25/5 105/115 °C temperature switch in
models 201.126 and 201.128
- In vehicles with large auxiliary fan
and 4-cylinder engine, the auxiliary fan should operate (except models 201.024 (AUS),(J) model year 85).
In vehicles with 5 and 6-cylinder engines, only the auxiliary fan should operate in the 1st stage. For models 201.024 (AUS), (J) and 201.028/034, then connect the 1-pole coupling at temperature switch S25/4 or S25/5 to positive. For models 201.029/034/035 ECE/CAT/126 and 128, bridge the 2-pole coupling at temperature switch S25/4 or S25/5. Auxiliary fan must operate in the 2nd stage.
At the same time, observe the direction of rotation of the auxiliary fan (clockwise).
4 Check fluid level in air conditioning system:
To do this, disconnect one cable at the pressure switch (S31/1), run engine at idle speed (> 750 rpm) and switch on air conditioning system. Clean sight glass (arrow) in receiver dehydrator. Observe sight glass and simultaneously connect cable to pressure switch (S31/1). Refrigerant level must rise shortly after the electromagnetic clutch is switched on and then flow through with no bubbles (i.e. refrigerant no longer visible).
!
In the event of severe refrigerant loss or an empty system, the voltage for the refrigerant compressor is interrupted by the pressure switch (S31/1). The power circuit is closed again when the pressure rises to 0.6 bar above the cutout pressure.
NOTE: If the refrigerant compressor fails to cut in, bridge the cables from the pressure switch (S31/1) and check the fluid level in accordance with paragraph 4. If the refrigerant compressor still fails to cut in, check the compressor cutout or the actuation of the compressor.
Checking
1 Heater switches (22 and 23) at position "0".
2 Set air distributor switch (24) to symbol [][] and air volume slide switch (S3) to the 4th blower stage.
3 Move temperature slide control (N19) to "max" and move lever (19) upwards to symbol [][].
4 Open left and right side outlets and switch on recirculated air switch (S24).
5 Insert a thermometer into the left or right center outlet (25).
6 Position a thermometer for the ambient temperature (workshop temperature) outside the vehicle approx. 2 m from the driver's side.
7 Open windows and close vehicle doors. Run engine at approx. 2000 rpm.
8 After approx. 5 minutes, take readings on both thermometers (center outlet air temperature and ambient temperature) and compare with the values in the table.
NOTE: The air outlet temperature at the center outlet must not exceed +3.0 °C. To test the temperature slide control and temperature sensor, refer to "Temperature Slide Control, Removing/Installing/Checking" Service and Repair
NOTE: If the system provides no cooling capacity although the refrigerant compressor is running, check the cooling capacity in conjunction with the suction/high pressure.