Air Conditioning - Checking With Test Cable

AIR CONDITIONING - CHECKING WITH TEST CABLE
as of 09/87






Note And Preparations For Testing
In-car temperature sensor (B 10/4) - Checking with leads
- Test Step 1
Outside temperature sensor (B 10/5) - Checking with leads
- Test Step 2
Evaporator temperature sensor (B 10/6) - Checking with leads
- Test Step 3
Left heat exchanger temperature sensor (B 10/2) - Checking with leads
- Test Step 4
Right heat exchanger temperature sensor (B 10/3) - Checking with leads
- Test Step 5
Coolant temperature sensor (B 11/7) - Checking with leads
- Test Step 6
Duo valve (Y21) - Checking with leads
- Test Step 7
Switch-over valve connector block fresh/recirculated air flap, 2-fold (Y 13/1) - Checking with leads
- Test Step 8
Left temperature selector wheel limit switch
- Test Step 9
Right temperature selector wheel limit switch
- Test Step 10

Preparations For Test Steps 11-24
Voltage supply to control unit - Checking
- Test Step 11
Left temperature selector wheel
- Test Step 12
Left temperature selector wheel
- Test Step 13
Right temperature selector wheel
- Test Step 14
Right temperature selector wheel
- Test Step 15
Negative activation of duo valve (Y 21) - Checking
- Test Step 16
Negative activation of coolant pump (M 13) - Checking
- Test Step 17
Negative activation of recirculated air switch
- Test Step 18
Negative activation of recirculated air switch
- Test Step 19
Negative activation of switch-over valve connector block fresh/recirculated air 2-fo1d flap (Y 13/1) - Checking
- Test Step 20
Air conditioning switch activation
- Test Step 21
Air conditioning switch activation
- Test Step 22
Auxiliary fan 2nd stage activation - Checking
- Test Step 23
Negative activation of a/c compressor - Checking
- Test Step 24





Special Tools:
Commercially available tester Multimeter e.g.,
- Sun DMM 5

NOTE: The test program is to be carried out when the cause of the problem is unknown, for instance, when the inside temperature set at the temperature selector wheel is not obtained, or when the a/c compressor fails to switch on. Before beginning with the tests, check fuses 1, 5 and 16.

Preparations For Testing:






Before testing is started, the ventilation blower for the inside air temperature sensor must be checked. Switch on the ignition and place a small scrap of paper approx. 1 cm2 (arrow) on the screen of the inside air temperature sensor. The paper must remain in place. If it does not, remove the glove compartment and check the ventilation blower (connections and operation).

1. Remove control and operating unit.
2. Remove front cover below the right side of the instrument panel and pull the 27-pin plug from the automatic temperature control control unit. Connect the test lead from the contact box with the 27-pin coupling from the wiring harness. The control unit remains connected until Step 10.

Test Step/Test Procedure:






Test Steps 1 to 4






Test Steps 5 to 8






Test Steps 9 to 15






Test Steps 16 to 20






Test Steps 21 to 24