I have spent the past three days pondering the ACC woes on my '84 300D (123). I just bought the car, so I don't know how this problem developed, but right now there is no response from any of the buttons on the automatic climate control unit. That's not true. I can get one response, but I'll tell you about that later.
Nothing on that unit makes the blower blow, and no I don't hear any clicks when I press any buttons. I took the darned thing apart and checked for poor solder as per the tutorial found here: http://207.210.95.34/~boostd/Climate/. Unfortunately, I saw nothing (and, actually, I didn't know what to look for since that tutorial is a little vague about that). So, there doesn't seem to be a problem with solder, but who knows?
Anyway, maybe you're thinking the blower doesn't work. It does, actually. I know because I can rig it up to blow by connecting a wire from the battery to the upper right pin of the connector that should attach to the Blower Resistor (none of these pins light my test light). When I rig this up, I get hot air out of the vents. Which vents depend on what I do with the ACC buttons (this is where the reponse comes in). When the empty circle button is depressed
(off), I do get hot air out of the center vents and the sides. When any of the other buttons are depressed instead, I get hot air out of only the side and defrost vents. Folks have suggested that this is vacuum-related, but I don't have a mightivac or the money for one right now, so I am hoping somebody will read this an recognize that the confluence of problems in the ACC is indicative of one, overarching problem which superseeds that of the vacuum.
By the way, I checked the heck out of the fuse(s), so that's not the problem.
Now, I live in San Diego. I have no interest in hot air coming from any vents in June, so this rigging up does not appeal to me. I also have no interest in running cold AC (I never use it in my other vehicle). I just want a fan to blow fresh air on me when I am driving.
None of the other threads about ACC seem to apply to me, so I ask you, strangers, have you any idea what's up with my ACC?
Mike Rancourt
ACC = strong college basketball onference; weak climate control unit.