Just for info I bought a 300 SD and the fan motor came on for a few seconds and quit. I checked everything and found no power going to the motor. After tearing the dash apart I finally pulled out the climate control and took it apart." WALLA" there was a trace on the board burnt in two. I hooked it back up, turned on the blower, jumped out the burnt trace and the fan cut right on. Might be something to look at if you ever run in to this. It seems there is a relay under the hood the climate control pulls in to start the blower. GOOD LUCK

 

 

At least you have version 3 of the climate and heating controls. I have a 450SLC with version 2 of the ACC automatic climate control. When it works is works great. I have owned the car 8 monts and three weeks ago I finally got it working so I have heat on all settings. There is a ACC Servo, which I found out Mercedes bought the patent and productions rights from Chrysler back in the 60's as they used this system on the imperial but dumbed it. I guess Mercedes, being Germans thought they could make if faultless. Well it is not. It still doesn't work perfectly, once in a while I will get a blast of cold air when the temp gauge is set at 85.

I found a company www.mercedessource.com that sells a manual kit for this servo business, it is really manual, they use manual choke wire to control the heat and AC, and it involves mixing the heat and AC to warm up th car is the AC is too cold, or when heating to pull the manual cable, in and out and prehaps turn on the AC to cool it off. I still think it is better then the "automatic". My son and I spent months fixing vacuum leaks replace, vacuum lines actuators, electirical connedtions, had the servo repaired twice the seond time at no charge. The nice thing about this manul system it is relatively cheap and you still use the dash mounted buttom., and the servo stays in place, allthe maunal system does is control the heat and AC output. I could probably make one myself with a old stype heater valve and some choke cable. but buying the kit is easier the running around looking for the right parts.

One one on these servo to insure heat inthe winter is to jump the aux heater pump and disconnect the ambient sensor on the firewall, you will get some much heat you can cook an egg on the dash. To control it you would have to stop and disconnect the negative ground jumper on the aux water heater. So that is out. as stopping and going to adjust the heating pattern is not a Mercedes way?

Glad you found a relatively easy fix for the system 3 heater and AC.

 

Well I took the climate control to work and fixed the trace that was burnt in two. Brought the unit home plugged it up, turned the fan on, let it run for awhile and it burnt the traces right back out again. Any Ideas as to why this thing is getting so hot ???

 

It is broken. Do you have the 3rd generation ACC in your car? The one without the big servo?

 

Do not know what type it is I just bought the car last Wednesday. I was just looking for some help on this. Not sure if the board just flaked out or if something else messed it up.