Hi there I have a1987 300d I have intermittent blower moter. When it works all speeds and everything works good. I have checked the motor itself and the electronic speed controll. The blower usualy works first thing in the morning but when I shut if off in usualy will not come back on if I repeatedly hit the all the buttons itmay come back on. Usualy it will come back if I turn key on and off wile driving. But not always itsnot ignition switch I don't think because all power in fuse box always works. And doubt its the controll buttons since I have tried 2 others and it acts the same. Any body had this.
Thanks mike

Sounds like you have a broken solder joint inside the climate control unit. I've had to fix every w124 and w201 that I've had. Just pop the bottom panel off of the climate control unit and reflow the joints for the buttons and thumb wheel. Unless you tried one that you know if fully functional, it's probable that both of the CCU's that you tried have had this problem. They all seem to.

OK I will check that since the one I tried was just taken out of a junker I have and don't know about it for sure. Thanks

Don't dismiss the ignition switch yet. There is a separate contact in it for the blower.

Also check the fuse for the blower. They can develop a small crack and become intermittent. Early W124's had it in the fuse box but it was later moved out to a separate holder and changed to a strip type fuse. Many early ones were modified to the later version due to overheating.

Could be the regulator, it's a pain to replace but sounds like you got down to the motor which is most of the battle.

OK thanks guys. My car had the fusein the pannel itook itout and wired up a seperate one. I took out the ccu and can't visually find anything.there is always powe and ground at the resistor terminals ifijump power to the small yellow wire the fan works. Even when the blower doesn't work when I cycle the ccu buttons I heart a relay click under the dash somewhere. But I can't find it. Mabyi should just put a potentiometer in the dash hookero the yellow wireon resistor forfan speed controll.