Hi,

I often read posts in this forum and appreciate the wealth of knowledge, but have never posted here. I am redoing my A/C which had several symptoms. It was not working properly, blowing out of incorrect vents, so I used a "Mityvac" to test the pods and ended up removing the dash and replacing them. The interior is working fine now. The other problem that I have had is that my fan is always on and only on low. I have a spare push button control unit and have switched it out, with no change, so I assume the push button unit is fine. (The fan is always on low, even with the switch turned to the off position and no matter where the fan is set). Since the fan runs, I assume the fuse is fine. I have pulled the blower motor and regulator and took the motor to the local motor repair shop. They tested the motor, told me the brushes still had about half their life left and that the motor was fine. I have plugged in the regulator and tested the voltage with the engine running and the a/c controls set on high, low and various settings. The output is always about 11 V. With the a/c set to off, there is a voltage of .5 to .6 V. I completely removed the controls (unpluged the two connectors to the push button unit) and I still get the same readings. I'm stumped. Could it be the Kilma relay...?

Thanks for reading my long winded post.

Wade

 

This is for whoever might read this in the future. The problem described below turned out to be the blower motor regulator. I am not sure why this would keep the fan from turning off, unless Mercedes engineers decided fail safe on was better than off. While at it, I found that the cover for the relays and electronics behind the batter was torn and the drains plugged due to my many pecan trees. I had trouble starting when it rained and it was that water was getting on the electronics. The moral of the story is maintainance and keeping the drains clean. The blower motor had about half of the brushes left, so I saved replacing them to another time, but did lubricate the bearings (bushings) with transmission fluid. It is nice to have a fully functioning a/c again. Total cost with vaccuum pods and regulator was about $300.