W210 Aux Fans
 

Hello everyone,

I have a question. I recently recharged my AC (it was blowing warm from drivers side vents) and no notice that my AUX FANS only cycle for about 2 seconds. They make about 3 revolutions and stop. It will wait 30sec to 1 min and cycle again. Car is at operating temp, I thought they should come on when the compressor comes on? Any thoughts.??

Put the pushbutton control unit in auxiliary test mode by pressing both AUTO buttons simultaneousely for more than ten seconds (it takes about twelve on my car). The engine need not be running, but the key should be in position 2.

Then watch the fans. If you see them cycling like this, the problem is either in the fan motor or the controller.

The fans don't start automatically with the AC, but turn on when any of several criteria are present. There are limits on refridgerant pressure and temperature and ECT which activate the fans.

I'm not sure if you have the N65 pulse-control module in your car or if you have the later fan control box.

Thanks Matt, will give it a try

With your strange symptom I would suspect that the version coding in the ACC module could be incorrect. Fans tend to act tweaky when the programming and hardware don't match. Sounds oddball but is more common than one would think. Need to have a high end MB shop check and verify the version coding in the ACC and possibly other modules.

His symptom is not so strange, if he has the N65 pulse-control module providing power to the M4 auxiliary fan.

It shuts down the fan if it detects too little or too much current, acting exactly as he described. I doubt it's a version coding problem.