AC Compressor stays on - PeachParts Mercedes-Benz Forum

Tanksowner · #1 05-21-2011, 02:01 PM

So I've been using my air conditioning more now that the temp is getting warmer and the sun is out FINALLY. My concern is that the compressor stays turning constantly even when I switch to economy setting. Strangely enough, it doesn't have this problem with the engine off. It switches back and forth no problem while the engine isn't running. However, once the engine's on, it either won't come on or it won't stop turning. Thoughts?

engatwork · #2 05-21-2011, 02:40 PM

Say again.

leathermang · #3 05-21-2011, 02:48 PM

Quote:

Originally Posted by engatwork

Say again.

LOL, it gave me a headache trying to visualize the situation....

Volvo Diesel · #4 05-21-2011, 03:04 PM

I had a similar issue at the end of last summer on my '85 300D. I don't quite follow what you mean about the compressor operating correctly while the engine is off, but I did have the situation where the compressor would engage no matter whether the ACC was set to economy or even switched completely off. After checking to make sure the ACC was operating as intended, my indy replaced the KLIMA relay, which cured the problem.

I purchased a new relay, since the old one was 25+ years old. I have no idea whether the old relay could have been repaired to function as designed. I think that '85 was the only year the W123 received the KLIMA system, but I'm not 100% sure on that.

Hope this is helpful,
-Chris

Tanksowner · #5 05-21-2011, 05:42 PM

Quote:

Originally Posted by Volvo Diesel

I had a similar issue at the end of last summer on my '85 300D. I don't quite follow what you mean about the compressor operating correctly while the engine is off, but I did have the situation where the compressor would engage no matter whether the ACC was set to economy or even switched completely off. After checking to make sure the ACC was operating as intended, my indy replaced the KLIMA relay, which cured the problem.

I purchased a new relay, since the old one was 25+ years old. I have no idea whether the old relay could have been repaired to function as designed. I think that '85 was the only year the W123 received the KLIMA system, but I'm not 100% sure on that.

Hope this is helpful,
-Chris

Forgive the lack of clarity. My intended meaning was that it would not switch between air conditioning and economy with the engine on. But if you had the key turned to the on setting without starting the engine, you would be able to switch between them. Perhaps replacing the relay will solve the issue then?

engatwork · #6 05-21-2011, 05:48 PM

How do you know it is switching if the engine is not running.

Volvo Diesel · #7 05-21-2011, 07:25 PM

Quote:

Originally Posted by Tanksowner

But if you had the key turned to the on setting without starting the engine, you would be able to switch between them.

I think the confusion stems from the fact that it's hard to see how you'd know the compressor is switching on with the key only in the accessory position since, to the best of my knowledge, the belt that drives the compressor doesn't turn when the key is in that position. That being said, my knowledge has frequently been shown not to be the best, so... Maybe you can hear a sound which indicates to you the compressor is switching on?

I'd suggest checking to make sure the ACC panel was functioning properly first. A number of years ago I had an issue that was resolved simply by cleaning the connections and resoldering something on the board. Next check out the KLIMA related "stuff," including the switch on top of the valve cover that cuts out the compressor when the accelerator is depressed past a certain point, and the relay.

In diagnosing my car's issues, my mechanic switched the relay in my car with a good used spare to determine that the relay was indeed the malfunctioning part. I then decided to buy a new relay, and the A/C has worked fine since. The relay I bought wasn't cheap, but I didn't price buying one from this site, I just had my mechanic order it and put it in, so I'm sure I paid a premium. In fact, my mechanic chided me for not just doing it myself after he'd diagnosed the problem, because I think he said the relay just plugs in somewhere on the driver's side of the engine compartment. At the time I was commuting 180+ miles per day, and being able to switch between the economy and cooling settings made for a more comfortable drive, and also made for better mileage, so I just wanted it fixed.

Good luck getting yours taken care of.