Climate control diagnostics on '90 - '95 R129 SLs

[bobterry99]

I've been looking for this for years and stumbled upon it. It comes from the manual for a Baum Tools CS1000 scanner which I downloaded a year ago. I don't own the scanner, but since the manual gives the meaning of all the DTC's it is very useful. This post is just for the ACC unit.

Reading Actual Values
1. Ignition to Position 2 with engine off or on.
2. Press the REST button and within 1 second press blower speed button 4.
3. The temperature window will alternately display the test step number (ex. "02 = in-car temp.) and the actual value.
4. Use the "F" and "C" keys to navigate to the different tests.

Test 02 = In-Car Temperature Sensor
Test 04 = Outside Temperature Sensor
Test 06 = Evaporator Temperatrue Sensor
Test 08 = Heater Core Temperature Sensor
Test 12 = Engine Coolant Temperature Sensor
Test 14 = Temperature Selector Wheel Setting
Test 18 = Vehicle Speed Signal (km/h)
Test 20 = Soft Top OPEN ("u") or CLOSED ("o")
Test 22 = Power Supply Voltage
Test 83 = Not Used
Test 84 = Blower Motor Voltage

To exit this test mode press "0".

Retrieving Stored Diagnostic Codes
1. Turn temperature selector wheel into the white area.
2. Ignition to Position 2 with engine off or on.
3. Within the next 10 seconds, press the "F", "RECIRCULATE AIR" and "REST" buttons simultaneously for 2 to 4 seconds.
4. The display will show the permanent DTC's stored. Press the "RECIRCULATE AIR" button after each is displayed until the display reads "END".
5. Press "RECIRCULATE AIR" button again and the intermittent DTC's will be shown. A square is shown after each of these DTC's to indicate it is intermittent. Press the "RECIRCULATE AIR" button again to see the next intermittent DTC and continue until "END" is shown.
6. To erase the DTC's: switch ignition from off to Position 2 and within 10 seconds press "RECIRCULATE AIR", "REST" and "UP" buttons simultaneously until "---" is displayed.

DTC codes: I will email a list of them to you if you like. There are too many to list here, but know that "1" = no DTC's in memory.

[waybomb]

Could you mail a list to me at waybomb@hotmail.com?

[Ronw435]

That would be great if you could email me the list on the codes. Sure do appreciate your response. I was going to just install a switch for the fans but hopefully this will tell me which sensor it is. There are two in the goose neck. Do you know which one operates the Aux fans?

Thanks again for the response.

Ronw4235

[bobterry99]

The codes are in the back of the manual downloadable here: http://www.benzworld.org/forums/r129-sl-class/1266535-diagnostics-sl-pre-94-a.html?.#post2342164.

There are two coolant temperature sensors side-by-side: one for the instrument cluster display and the other for the climate control. The closest to the engine block is for the climate control.

[jmerc6]

Bob,
I've got a '95 SL500 that I wanted to run the diagnostic, but when I tried I got nothing. Does the above procedure work for the SL500, MY '95?

[bobterry99]

Yes. It works for all R129s through MY1996 except for the first cars manufactured in 1989.

Possibly your controller is not original and came from one of those very early cars.

[jmerc6]

Thanks Bob, nothing surprises about this car.

[rcappie4]

Will this work on a 2000 sl500? Thanks

[97 SL320]

Sort of. On 97 + , with the climate control turned on , key on ( engine status does not matter ) , press and hold the REST button until the screen flashes 01 and some other number. This is the data screen, use the fan + and - to scroll through the screens.

Dig around on this forum, the list has been posted. There is also a way to get diagnostic codes as well.

On my 97 SL320 , the climate control is the same as a similar year C280 ( not the C220 / C 230 as these had manual controls ) To swap a C and SL unit, the version coding must be changed and there is a button push to accomplish this as well.