Hi all. I have a 1995 C280 with blower motor and/or CCU problems. I've ordered a used (but fully tested and guaranteed) CCU, which should be here by Friday. I've acquired a blower motor in very good condition. I had replaced the blower motor regulator a few months ago, so it *should* be OK. And if not, at least it's not a difficult or expensive repair.

I've done a lot of research and learned that certain voltages should be seen at the black 4-pin connector, into which the white connector from the motor & regulator mates. There should be 12V from pin 1 (GND) to pin 2 - and there is. The speed signal voltage from pin 1 to pin 3 should vary from 0V - 6V, depending on the position of the fan switch and a few other factor. So far, so good. BUT, I was told that I should find 0V on pin 4 (IGN?) with the ignition switch in OFF, and +12 with the ignition switch in RUN. That voltage isn't there. The source of the above info said that not getting 12V at pin 4 with ign. sw. in RUN meant a blown fuse (#33 or #35, perhaps?) or a wiring problem between the ignition switch and pin 4.

HOWEVER, the wiring diagram I found at diakom.ru shows pin 4 of the blower motor connected connected to both the cabin temperature sensor fan and pin 2 of the Switchover valve block. Is that correct? If not, how do I determine where the 12V from the ignition switch goes. In other words, how do I track down the point where it fails? The wire connecting these 3 points is Gray/Red, according to the diagram, in case that helps.

There are several electrical problems with the car, which started all at once. Insulation broke down on the small wiring harness that runs underneath the car (as in, passing down from the engine compartment, going toward the center of the car near the transmission pan and beyond.)

The failed wiring harness caused the K8 replay to burn out. Our mechanic replaced the harness and the relay but wasn't able to diagnose the rest of the trouble. As of right now, you can't start the car unless you hold the door-lock switch on the console down while turning the key. Central locking and alarm functions were DOA when we bought the car. I plan to replace the ATA module as soon as I find one for sale.