Hey guys, just bought a 1987 300D Turbo with 250K miles.
RUNS GREAT fast and solid.
3 problem with it
1. fixed no cruise controled, replaced some old vacuum hoses and cruise control works
2. NOT FIXED sunroof doesn't open I hear the cable moving so maybe a cable problem, will look into it later, but here is my real problem:
3. NOT FIX - A/C not working, compressor and clutch good. The car has been recently converted to R134a. The diagnostic is - NO POWER TO AC COMPRESSOR. I have been told that the ACC unit inside the car is not good,
all the buttons work fine, fan, heat etc.
I just open the fuse box this morning myself and saw that the fuse no. 6 is missing - checked what it was for , horn, turn signal and I forgot what else, anyway I tryed to replace the fuse and all my dash board lights went on, as if you try to start the car, including the buzzer box. the horn and turn signals work fine though with out that fuse, but they work all the time, even when no key in ignition.
The auxiliary fan comes as soon as you try to start the car and never shuts of unless you turn the car off. One mechanic told me that it is a short somewhere that's why the fuse 6 is always hot.
Thanks guys and please ask me any additional questions. I'm on my way to the benz dealer to buy a new ACC unit, I live in Sacramento California and the temp is about 103F today

Who diagnosed it and how did they come to this conclusion?

A mechanic at Imorts specialists shop in Sacramento

OK, then.

Hopefully he nails it. But, it's a complicated system with all kinds of sensors that can prevent a compressor engagement.

I recently spent an entire weekend chasing a similar situation.

You purchasing a brand new pushbutton unit?? That's got to hurt.

The dealer doesn\t have the ACC unit in stock, anyway I was about to walk away from the $696 bill anyway
I took the ACC unit apart, looking for unsoldered wires, connectors, items etc

Have you considered a rebuilt ACC unit? The cost is more like $275 plus a core deposit, and they are fairly simple to install. Most of them have some kind of warranty.

Yes, That's what I will do, but I would really want to know for sure that is the problem. I have read here a lot about defective ACC units, from fan blower problems to not blowing any kind of air at all. Mine works fine, everything on it, except when I turn it to cold max AC compressor doesn't engage. I say again AC compressor works fine when tested. Also the same mechanic replaced the AC relay controller with another one and still no power, then he diagnosed the ACC unit to be faulty. Also how come the aux fan is always on and the fuse no. 6 is crazy? Any idea? Thanks a lot I really apreciate all this help.

Bump

Brian I have a 1987 300D as well and my AC problem is a bit different than his. The compressor engages and cools but kicks off once you engage the accelerator. So as long as I'm already accelerating down the highway she blows cool but the moment I stop and then re-engage the accelerator she kicks off. Any ideas on whats going on here?

Bumping this up for the heat.

I replaced my serp belt yesterday, and also flushed the power steering fluid. In the process I got some on the belt so now it slips a touch. The compressor runs for 3 seconds then shuts off. I'm hoping the mismatch in RPMs is the only reason for this as the AC worked great beforehand.

EDIT: As it turns out I installed the belt incorrectly. Oops. It was slipping on the crank.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
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