240D fickle A/C compressor - Page 2 - PeachParts Mercedes-Benz Forum

sailor15015 · #16 08-07-2006, 10:56 PM

There is a sensor on the evaporator that cuts the compressor out when the evaporator gets to a certain temperature. Its about a foot to the left of the expansion vavle and its insulated. I've never heard anything about a compressor cycling to maintain a pressure. Certainly could be though.

gene2 · #17 08-08-2006, 07:22 PM

slcom1983 email me at gene@usonet.net and I will send some pictures of A/C relay and how to by-pass it with a fuse.

Gauge · #18 08-08-2006, 08:30 PM

Quote:

Originally Posted by Slcom1983

Still sorting out the small bugs in my new-to-me 240D. I love the manual climate control (verses the push button debacle in my 300D) but it has a peculiar quirk. Most times when I move the blue temp wheel to the cool area and turn on the fan, the fan comes on in fine order but the compressor does nothing and blows just ambient air.....however a while later driving down the road I may try again and feel the compressor kick in and the cooling begins. I thought at first that perhaps the compressor would not engage because of the low pressure switch but surely it wouldn't come and go as it's doing. The only thing I could find by searching related to this problem was that the ignition key sometimes affects the climate control. Any help on this intermittent problem?

WOW! I have the EXACT SAME PROBLEM with my 1983 240D. AC sometimes chooses not to work. I tried solving this problem too thinking that maybe the freon level was low. I had the pressure tested and it was fine. After having the system completely checked, I gave up, learning to live with the AC hesitation, as my experience has been that it may take awhile, but the AC always comes back on. My delay has never been longer than 3 to 5 minutes.

Slcom1983 · #19 08-08-2006, 08:32 PM

Quote:

Originally Posted by gene2

slcom1983 email me at gene@usonet.net and I will send some pictures of A/C relay and how to by-pass it with a fuse.

Done.

Slcom1983 · #20 08-13-2006, 09:37 PM

Ok folks...I got back to the 240D this weekend. Here the results of the tips. (1) When I jump across the low pressure switch, the compressor does not kick in. (2) There is 12V at the compressor with the controls set for the A/C to come on, and no voltage at the compressor when the A/C controls are set for the A/C NOT to come on. (3) Switching the relays doesn't result in any change and (4) A jumper wire across the relay socket as Gene suggested to try also did not cause the compressor to kick in.

Since when the controls are set for A/C, there is 12V at the compressor leads but the compressor does not pull in, does this mean the clutch and/or entire compressor is bad? Can a clutch be an intermittent problem? Thanks for you continued help.

gene2 · #21 08-14-2006, 06:59 AM

O.K. If you are getting power to the clutch at the right time. And the clutch does not kick in... try one more thing, unplug the clutch. With the key OFF. Use a jumper wire and go from battery to clutch, if clutch does not kick in, you know it is the clutch.

Slcom1983 · #22 08-14-2006, 09:09 AM

Quote:

Originally Posted by gene2

O.K. If you are getting power to the clutch at the right time. And the clutch does not kick in... try one more thing, unplug the clutch. With the key OFF. Use a jumper wire and go from battery to clutch, if clutch does not kick in, you know it is the clutch.

I'll give it a try. When I connect a jumper from the battery to the leads on the compressor, do I need to be concerned about polarity? If so, do you remember which spade connector on the compressor is the pos and which is the neg? (left being passenger and right being driver sides).

gene2 · #23 08-14-2006, 09:26 AM

I will check mine later today and post.

gene2 · #24 08-14-2006, 10:47 AM

The brown wire is ground. It is on top if at 3:00 The clutch will kick on either way. Do not know if you should, I am just saying it will.

Slcom1983 · #25 08-14-2006, 08:34 PM

Thanks for all the help...especially Gene2. With the car cut off, I connected wires directly to the compressor and then touched the battery terminals...NOTHING!...not even a click. Does this mean the compressor clutch is bad? It's very odd, but as soon as this test failed I drove up the road and the compressor started working and cooled like a champ. When I got home I turned off the A/C and tried to turn it back on and it wouldn't. This is really a mystery...or is it?

KPMB82 · #26 08-14-2006, 09:30 PM

So you have 12V at the clutch. You need to check the resistance af the clutch coil with an ohm meter. Check with one lead on each of the terminals. I beleave it should be about 4 ohms. Should be good or it would never engage. Next measure the air gap between the front plate and the clutch coil with some feeler gages, your gap should be about .0025 of an inch. If your gap is too large the coil can't pull the plate in to engage the compressor.