CLK320 Air Conditioning Cutting Out
 

2001 CLK320 128000 miles.

When I turn the air on, it blows cold air for about 2 minutes, then the compressor stops turning and it blow regular air.
If I stop the engine and restart, the same events repeat.

I posted this problem about a year ago, and MB Doc suggested a defective evaporator sensor.

Before I take the bottom of the dash apart to test the evaporator sensor, I would appreciate any insights on numbers that could be out of normal range. The evaporator temperature at 200 (?) degrees is extremely suspicious and could well be the culprit. What would it show on a system working properly? Where is terminal 58d ?

Thanks

The diagnostic codes on the climate control show the following:

01 - 103 In-car temperature sensor
02 - 92 Outside temperature sensor
03 - 69 Heater core temperature sensor left
04 - 69 Heater core temperature sensor right

05 - 200 Evaporator temperature sensor
06 - 172 ECT sensor
07 - 8 Refrigerant pressure in bar
08 - 100 Refrigerant temperature sensor

09 - 8 Menu for activation
10 - 0.8 Blower control voltage
20 - 0 Control current for auxiliary fan
21 - 7 Engine speed

22 - 0 Vehicle speed
23 - 0 Terminal 58d, corresponds to 99% battery voltage
24 - 14.2 Battery voltage
40 - 8 Software status

41 - 5 Hardware status
42 - 232 Version code 1 number code
43 - 14 Version code 2 number code

Evaporator temp sensor is the problem!

Circuit 58 is for the lighting of the unit.

Just to throw another idea out there.... On my '87 300D, the clutch was going out on the a/c compressor. There is a sensor on it that keeps track of the rpm and if it is significantly off of what it should be in relation to the engine rpm, ie slipping or locking up, power is cut off to it. When you turn the key off and restart, it resets it. This is done to keep from burning up the belt in case it is locking up. Check the clearance on the a/c clutch. Also, check to see if you have oil getting on it causing it to slip.

It was the evaporator temperature sensor, as mbdoc diagnosed.
Took me about half hour to replace it.

Sorry for posting this more than a year too late.

Thanks Harry,
Could you describe the replacement procedure? thanks.

If you are suspecting the evaporator temperature sensor, do the diagnostic display early in the morning, before the car has been driven or parked in the sun etc. The first five numbers should be about the same. If the evaporator sensor is dead it will show a weird number, like 200 in this case.

Carefully remove the lower dash panel on the left side. Remove the two screws holding the OBD2 connector and leave it dangling there. The sensor is on the left wall of the evaporator unit and may be impossible to see with your head the right way up - unless your head turns like in The Exorcist. I had to lie on my back to see it. Unplug the connector from the temperature sensor, and pull the sensor out. The only thing holding the sensor there is the springing action of two tabs on it.

While I was there I smeared a little grease on the ratchet mechanism of the parking brake.

Thanks very much.