Wacky Air Conditioner - PeachParts Mercedes-Benz Forum

#1 12-11-2003, 07:53 PM

I just purchased another diesel Benz. This time it is a Gold 84 300D turbo with 80,000 miles for a mere $1500.00. The car is beautiful, even came with a car cover. Everything seems fine (drum roll please) except, the air conditioning system, and the clock and tach is not working at all. I have spent the last two days reading old posts here and really have enjoyed the information. I qanted to ask a couple of questions before I break out the tools.

Here's what is happening. The air will only come on when the car is first started and will run for only 4-8 minutes, I timed it several times. It will only run on the minimum temp setting, any other setting and nothing. If you try to change it while you are getting the initial blast of very cold air, it stops dead, nothing at all. If you push any of the control module buttons, try to adjust the temp or the fan speed, it stops and the seat belt light will come on for about 3 seconds then goes off. The air will not work until the car sits for awhile and is restarted.

I read earlier that it could be the mono valve and/or the climate control module.

Any other suggestions?

leathermang · #2 12-11-2003, 08:09 PM

"initial blast of very cold air," That is a wonderful place to start...
I suspect you are having a vacuum/ push button panel control problem. And the shop manual for trouble shooting them boggles my mind...but I think you are way ahead of what most people start out with if you have cold air at any time... your job is now just to get control of it...

#3 12-11-2003, 08:14 PM

It's o.k. right now when the weather is a nice 70-75 but when summer comes I'm going to get cooked. I live in South Florida and the temp is usually 95 with 95 humidity by June.

I bought the CD ROM for the old 126 I had, do you think it is the same?

I read an article earlier where a guy pulled the control unit and re-soldered it. You think it is in the module?

leathermang · #4 12-11-2003, 08:29 PM

I don't know much about Mercedes cars... but what I do know is strictly about the 123 ....
Sorry..... but someone that does know is bound to stop by and post with some good suggestions...

dmorrison · #5 12-11-2003, 08:46 PM

You need to be more specific when you say runs or does not run.
Compressor running or not and when?
Fan is it running and that is whats stopping?
Does the fan continue to run while the buttons are in low and is the air cold?
answer these and then we can move on to other questions.

Dave

#6 12-11-2003, 09:42 PM

It seems, and I have not pulled over and got out to listen yet, that everything stops, the fan and the compressor both. Normally you will feel a minor power drain if the a/c is on, when this happens there is no power drain. It almost as if I turned it off. As I mentioned earlier, if I press any buttons or turn any dial, the seat belt light comes on momentarialy, even after the a/c stops.

Also, when it quits I put my hands in front of the all the vents, nothing.

Thanks again for all the info.

BoostnBenz · #7 12-11-2003, 10:47 PM

I'm not sure on your particular problem but it sounds like you found quite a great buy, good bargain hunting.

I don't know if it'd be the climate control, in a couple weeks I'll have a page on how to resolder it. I had a problem with my fan shutting off from time to time (normally after bumps), and it isn't the motor brushes. I resoldered it and no more problems. Also there is a 123 factory online manual posted there.

kerry · #8 12-11-2003, 11:04 PM

If I were in your situation, I'd go to the local pick and pull, buy a control panel for $5 and plug it in to see what happens.

#9 12-11-2003, 11:16 PM

Ya Kerry,
I thought the same thing, if I could get my hands on a control unit and plug it in and it worked it sure would answer my questions real quick. I will make some calls tommorrow to see if I can find one. The local salvage yards are a little expense here.

BoostnBenz,
I love the idea of fixing it yourself. I can't wait for the instructions on resoldering it. I spent 7 years in the Navy fixing stuff, this can't be to hard. Ever fix one of those Becker radios? They always seem to die.

#10 12-11-2003, 11:18 PM

Why are fat girls like mopeds?

They are fun to ride but nobody wants to be seen with one.

BoostnBenz · #11 12-11-2003, 11:38 PM

One of the first things I did with my 300Ds (I had one before this one) was to rid of the factory radio and put a CD player in, so no I don't know how to fix the Becker.

That must be nice to get a part like that for $5 there are no local MB parts yards, I've called dozens of yards in my county and a few surrounding counties to find nothing. When I finally find one that has a car it is like a late 70s 240D and they expect more for one part than I'd pay for the whole car.

jhal · #12 12-12-2003, 03:17 PM

Check the fuses for you climate control. They get old and intermittant. Sounds like one is heating up and opening (breaking the circuit). Mercedes fuses are notorious for this type of behavior.

BoostnBenz · #13 12-12-2003, 03:22 PM

Valid point, I just threw all of my MB fuses away and put copper ones in there instead. I have yet to have a single problem, my old aluminum fuses were doing funky things at odd times so I rid of them. It was only like $7 for new upgraded fuses, enough to do a couple cars and still have extra!

leathermang · #14 12-12-2003, 04:40 PM

I must be losing my mind.... yall feel free to tell me that if that is the case....
BUT....
I have the factory shop manual for the heating,air conditioning,and automatic climate control... and I went to look at it when yall started talking about soldering, easy plug in to test, etc....
THis is a VACUUM OPERATED SYSTEM.... vacuum to electrical switch, vacuum to vacuum actuators, etc...
ANd I promise you that the diagrams and testing on this system is horrible... I hate to be a downer on this... but my 81 wagon switches had a mind of their own... like HAL in the movie 2001.....so before heading to the parts places I suggest lots of reading on the forum... and maybe picking up one of the proper manuals....

kerry · #15 12-12-2003, 05:09 PM

You've lost your mind. He's talking about an 84. It doesn't have the diabolical ACC like the earlier models but it still using electric switches coupled with vacuum actuators. You still have your mind when you mention how hard it is to troubleshoot these systems. That's why I mentioned earlier that a trip to the junkyard and some parts changing may be the easiest route.