Mercedes 190 E a/c problems

[Scott_in_WVA]

Thanks to all of you!!!!

 

[centex]

I only looked at Mercedes, Porche, Audi, and VW. I drove a VW for 100K miles but it was really a crappy car. Fortunately it did not have too many things to break. It was good on tires though. The Porches were falling apart in the showroom around their outrageous price tags. I had two friends who had Audi's and they both had some bad problems. I sat in a 500HP Audi at one of their factories in Germany. It was an impressive car with an impressive price but given my friends' experiences I would not have wanted it. I wanted a BMW but they started out as an inexpensive drivers car and I found it hard to think of them as being worth what they cost now but then I don't think any car is worth what they cost now. I now only buy old Japanese cars to drive. They seem to run forever and almost never break which is fortunate because the parts are very expensive. I think my 1972 Corvette is still the best car I have owned. I bought it new and have driven it for 350K miles and it never broke down on me until I got close the 350K miles. I finally had a rear wheel spindle break and had to call a tow truck. Fortunately the heavy duty disk brakes on the car kept the wheel from comming off. I would like to see a modern car's brake caliper do that! The worst car I have owned was a 1967 GTO. It was a piece of junk from the gitgo and I could not ride in it for 30 minutes without getting the worst back ache from the seat.

 

[karmakanic]

Hi Scott,

The a/c system used on the 190 is an unusual system. Basically MB tried to design an auto climate control system that used electronic control of the a/c system and mechanical control of the heater system. They mix the cold air and the heated air to get the desired vent temperature. To do this, they needed a feedback potentiometer in the heater circuit (which is vacuum controled) to tell the a/c system what the heater system was doing. Your problem likely is coming from this feedback potentiometer That is why it blows warm air when it acts up. These potentiometers were notorious for causing the symptoms you describe. The problem is, they're located on top of the heater housing, just underneath the dash covering. To replace them, the dash has to be removed.
There is an adjustment on them, which can be made with the dash in place, if the mechanic knows the tricks to get access.

Now, I'm not saying this is your problem for sure. Other things, like in car temp semsor, outside air temp sensor, push button control unit, ect. can cause similar symptoms. It will be necessary for someone to work with the car until the problem occurs. At that point, a few quick tests by someone who knows the system can determine the problem part.

Frankly, the dealership is not the best place to get a problem like this resolved. For one, the dealer techs are not inclined to spend the time necessary to get the problem to occur. They take it for a drive around the block and if the problem doesn't occur they send it back to the dispatcher with "no problem found" And the turnover in a dealership means most of the mechanics were still in high school when that car was built. The old guys in the shop know to run and hide when the dispatcher shows up with a 190e a/c problem, so the less experienced mechanics get assigned to the job.

My .02 advise is to hunt up an independent shop that's been around for a while and specializes in German cars. There's usually one around, since although Mercedes is the best car built in this world, they do break pretty often.

HTH
Dave Perry aka karmakanic

 

[Scott_in_WVA]

Thanks Dave....
I appreciate the info/tips and advice.....there is a foreign car specialist nearby...I will call him.
Scott

 

[Rowski]

Scott

Dave's advise is most excellent. As Dave mentioned the a/c system is very unssual in that uses both electric and vacuum. It's kind of like the the feed back carburator, great when it works... a pain when it doesn't. It would be nice if you find out whether its the compressor control that isn't working or the actual blending of the air. As an example the compressor will not run if the coolant temp is above 115C, the low pressure switch is open, the engine is running at full throttle, the compressor clutch speed is different than engine speed. So if any of these sensors are not up to snuff then no (or intermittent) a/c compressor. There are also many other things on the heater side as well. Another thing that comes to mind is the the conditions of the vacuum lines to and in the climate control system.

You might give <A target="_blank" HREF=http://iatn.net>iATN</A> a try use the shop locator to find a good shop. I use iATN a lot for work. If you need more info about your car's a/c system I have a copy of the wiring diagrams, etc. Send me a private e-mail.

Lets us know how you made out!

 

[Scott_in_WVA]

Derek,
I really appreciate what you have told me and Dave as well..I feel like I am getting somewhere now.
If I need the diagrams I most certainly will e-mail you.
Thanks again
Scott

 

[karmakanic]

Hi Dereck,

Thanks for the kind words.

Nice to meet a fellow iatn member here.

And Scott, do keep us informed how it goes with your problem. I also would be glad to help by email if needed.

Sincerely,
Dave

 

[Scott_in_WVA]

I am still working the a/c problem...been a busy summer.But plan on calling a foreign car repair specialist Monday.I have not drove the car that much.When the a/c works it works fine.