Simple forced ops of ACC - PeachParts Mercedes-Benz Forum

JHZR2 · #1 09-05-2012, 05:32 PM

Hi,

Ive been working on my 82 300CD for a while and started it up today for the first time in about a year. Started right up and ran like a top. Only issue - AC wouldnt come on. But it isnt just the AC, no fan either... So Im thinking ACC issue. Worked fine when I put the car away (hopefully that doesnt mean a mouse ate the wires!!!), and now nothing, no sounds of any kind, even a vacuum hiss, when any buttons are pushed, and of course no air flow, conditioned or not.

I want to get the ac blowing ASAP to circulate the system, but dont have the time or energy right now to do a lot of tearing of the system apart. Is there some "topside" jumpering, with the ACC connected or not, that I can do as a quick fix to at least get the fan blowing and compressor engaged. I dont care about heat or whatnot.

I have an old ACC in the basement, which may not work either. Im happy to buy a refurbished ACC from Phil, but would like to get the system blowing in the short term first...

Thanks!

carnut · #2 09-05-2012, 07:35 PM

First thing on ANY german car is to check ALL fuses with a test light, then rotate them in their holders. The old aluminum fuses would corrode and not pass current. If I remember correctly there are fuses over by the passenger side of the firewall underhood that control fan operation. Under the fuse box cover should be a listing of fuses, amperages and what they control. If it worked before you have a corroded fuse most likely.

JHZR2 · #3 09-05-2012, 08:28 PM

Not to sound rude but this isn't my first time to the rodeo. I've had a lot of w123s and are fairly familiar with their weaknesses and troubleshooting. Checking the blower fuse was the first thing I did because they are prone to high current draw (MB even offers a supplemental strip fuse kit for this for that reason). All the fuses are clean and great. Alternator charges, battery is strong and in good health.

The ACC isn't known for reliability and the solder joints go bad. That's why my best guess is that it is that. I have another questionable ACC to swap in, but iirc, it doesnt work. So I'd like to be able to bypass to some fan setting and the compressor on to cycle the system.

If the fan blew, I'd start diagnosing the AC charge and whatnot, but since NOTHING happens, once I find 12V at the ACC connector terminals, I'd like to be able to jumper to test the fan, compressor cycling, etc.

carnut · #4 09-05-2012, 08:41 PM

Not to be rude but the fuse checking was not mentioned in the original post. I have no idea of your mechanical abilities. I was simply stating the basic thing to check before any parts were replaced. These posts hopefully help others as well, not just season ticket holders to the rodeo

as you and I are.

JHZR2 · #5 09-06-2012, 12:14 AM

...And magically the fan started blowing again when I started the car up another time to do a few things... Weird.

That tells me that it is a bad solder joint on the ACC.

Unfortunately the AC didnt kick on, which is a real bummer... I am guessing that it is out of charge, which is unfortunate... The AC has worked great and blown cold and perfect since I got the car.

I have gauges, but I use them on 134a, and am a bit hesitant to put R12 in them...