Another W126 heater-blower/porcupine/monovalve thread

[airbus]

I did a search, but I couldn't find anything on these weird symptoms:

Cold starts, CCU on auto: nothing happens, even after 5min and engine warming up. Defroster doesn't do anything, either. However, if I put the fan on high or CCU on defrost before I start the car, it works immediately. When warm outside or warm starts, everything works like it should for a while.
When driving and CCU on auto, blower sometimes stops and won't come on again. Same thing on low fanspeed. When blower motor is stopped I can hear a relay clicking every couple of seconds.

I don't think it's the CCU since I can hear relays clicking and flaps moving when I change settings.

I pulled the blower motor and tried all possible CCU settings while holding the motor in my hand and of course everything works, put it back in, same ***** like before.

Any ideas?

[deanot442]

I had VERY similar symptoms in my 87 SDL, and the problem was some bad solder joints on the CCU, specifically the fan control switch. If you are inclined enough to remove it and re-flow or add some solder, to as many connections as you can reach with your iron, I think you will be pleased with your results.

[airbus]

Thanks a lot, deanot442, you were right. Since I'm not so skilled at soldering, especially at that scale, I got myself a "new" CCU from my local pick 'n pull to test and it works. Weird, though...