I'm just starting a new thread although I think that my problem may be relating to my overheating problem.

The EC light on the climate control on my 2001 S500 is stuck on.

This means the A/C is not working so I'm cooking in the car at the moment.

I'm going to go through fixing this this problem.

Background.
My electric fan control module had to be replaced recently. The Car overheated to a point where I had to pull over and let the engine cool. The indicated temperature in these situations is >130 degrees C.

I'm told that the error needs to be deleted from the AAC (auto air conditioning) control module. This is different to the engine control module. (so I am told). And that you can only do this clear, with special software (star diagnostic). (not my off the rack, read and code clear device from china).

 

the first thing I will do is check the fuse.

It's fuse number 23. 10 amps. Located in the left engine fuse and relay box.

The next step will be get the AAC code cleared. I don't know of anyway to do this except taking it to an air conditioning specialist or MB. Does anyone know where I can get a diagnostic unit that will clear this code from the AAC control module?

Then I'll need to check the refridgerant pressure and temperature sensor. The sensor is located on the receiver Drier at the front left of the car.
Refrigerant temperature must be between -40 and 100 degrees. Outside of this the system turns itself off
Pressure of the system must be between 1.75bar and 30bar. Again, outside this, the system turns itself off.

Engine coolant temperature also sends a signal to the AAC control module. Temperatures above 127 degrees cause the compressor to switch off. This is what I think my problem is. The car has hit above 127 degrees several times over the past week. I believe this is causing the computer to error and not allow the AC to work. Thus the EC light (AC off light) being illuminated all the time.
Another possibility is a faulty temperature sensor. I doubt this is the problem but will keep an open mind. (temperature on the instrument cluster seems good)

 

fuse checked and looks good.

I'm off to the MB dealer to have the DTC ('Diagnostic Trouble Code') erased from the climate control (KLA) system memory.

If this doesn't fix the problem, then I'll need to start looking at all the other AC components.

 

check your WIS again. this is wrong data.

but won't turn on the EC light.
it will go back to normal operation after the temp goes down.

 

Just Checked my WIS. These are the figures quoted. Maybe my WIS needs to be updated?

I've just come back from MB.

He ran the short test on the AAC and cleared the system.

The AC now runs well.

Aparently the system code that caused the problems indicated low refrigerant level. I only managed to speak to the technician briefly. He claimed that even though the code indicated low refrigerant, he didn't think this is what caused the problem. He felt that it was an problem with the evaporator / condensor sensor.
From reviewing WIS, these are separate sensors. I'll investigate it the AC goes out again. At the moment it's running fine.

It's also good to know that overheating the car only temporarily disables the AC compressor. thanks for the info.

If this problem comes back, I'll start posting to this thread again.

Cheers.

 

Just to add. The above took 20min and MB charged me 40GBP ($70USD).

 

Had the same problem..code that was present was for the ETR Switch (B1256)...I'm going to charge the system (was a little low) and see if the light stays off. Does anyone know where the ETR Switch is located?