86 SDL A/C compressor running wild - PeachParts Mercedes-Benz Forum

AlanTbird · #1 02-16-2008, 08:57 PM

It's been in the 70s here and last week we had some rain and I had to use the defog. when I turned it on the compressor made a rattling noise for a few minutes and then the noise stopped! A few days later I noticed some water dripping under the tranny and opened the hood to find the a/c low side hose all frozen up and the compressor running with the system turned off!
I disonnected the wires at the filter dryer and it still kept running.
I had to remove the plug from the top of the compressor to get it to stop.
I hope the main control unit is causing this as I still have the old one I replaced about a year ago when I had no heat.
I assume the wires at the filter dryer are not just a simple loop to the compressor but sends a signal to the main unit to start/stop it?

Just trying to find some info on what may be the problem bfr I wiggle the main unit out of the dash...........not fond of pulling on the wood trim and sutch if I dont have to!

All the other functions on the control unit seem fine.

Any and all adivise will be greatly apprecitated!

Brian Carlton · #2 02-16-2008, 11:20 PM

Find the Klima relay.

It's about the size of a large pack of cigarettes and lives between the two firewalls just in front of the driver. It might say "KLIMA" on the cover if it's original.

Pull it out of the sockets (pull hard).

Find socket #10.

Connect a voltmeter with the positive lead to the positive battery terminal and the negative lead to socket #10.

Turn the keyswitch to position #2.

With pushbutton numbers 1,2, or 3 depressed, you should see 12V. With pushbuttons 4 or 5 depressed you should see 0V.

Report back with results.

AlanTbird · #3 02-23-2008, 06:47 PM

Found it, it does say KLIMA on it and I get as you said if from the left to right.

#1 12v
#2 12v
#3 12V
#4 0 v
#5 0 v

now what?

Brian Carlton · #4 02-23-2008, 07:09 PM

Quote:

Originally Posted by AlanTbird

Found it, it does say KLIMA on it and I get as you said if from the left to right.

#1 12v
#2 12v
#3 12V
#4 0 v
#5 0 v

now what?

If the problem remains, the Klima relay is NG. It's not opening with a proper signal from the CCU. The CCU is confirmed to be good by your tests.

Naturally, be absolutely sure that #4 or #5 is depressed before you condemn the Klima.

babymog · #5 02-24-2008, 09:35 AM

It might or might not apply to your SDL, but random compressor and blower operation (even with the CCU OFF button pressed) is a typical failure mode in the '87 300D/TD original CCU, and it is the CCU / button unit in the 124.

AlanTbird · #6 03-01-2008, 11:35 AM

Ok so I got another KLIMA and its still running wild! Was surprised to see the AUX fan cycling but anyway....Unless theres an other thing to look at I will be swapping back My old CCU and could use a link to a thread for the R&R procedure. I kinda remember the radio and ashtray coming out but with all these children , I get confused somtimes!
Its already in the 80s here and the SDL has the best A/c of all of them!

Brian Carlton · #7 03-01-2008, 11:55 AM

Quote:

Originally Posted by AlanTbird

Ok so I got another KLIMA and its still running wild!

I'm not understanding what "running wild" means.

However, if your previous tests were valid, the CCU cannot be the culprit. It's functioning properly by switching the #10 socket.

I did have a CCU that would engage the compressor in the economy setting...........on occasion. So, if your data is good on one day.........and the compressor does not engage..........the data might be different the next day. This would point to the CCU.

If you want to remove it, first remove the ashtray (two phillips screws in the bottom).

Then there are two screws on the very bottom of the wood panel (pointing upward). Remove those.

Slide the panel downward about 1/4" and it will free itself from the dash and you can then remove the five plugs and fiber optic lights that sit above the CCU.

Now pull the panel and CCU forward and remove the large plugs on the sides.

AlanTbird · #8 03-01-2008, 08:43 PM

At the begining of my thread I explained that the compressor wont shut off unless I unplug the plug on top of it. Since learning about the KLIMA I can now stop it by unpluging that!
When I put the new klima on at first the comp. did not engage but then once it did it wouldnt shut off again. Also the Klima seemed very warm to the touch when I went to remove it!
I've done the #10 post test several times and its always as it should be.
I wonder of something is grounding/shorting somewere were it shouldnt be.

Brian Carlton · #9 03-02-2008, 11:21 PM

Quote:

Originally Posted by AlanTbird

When I put the new klima on at first the comp. did not engage but then once it did it wouldnt shut off again. Also the Klima seemed very warm to the touch when I went to remove it!
I've done the #10 post test several times and its always as it should be.
I wonder of something is grounding/shorting somewhere were it shouldnt be.

The Klima has a couple of relays inside so it's normal to be warm to the touch.

While it's possible that you have a short somewhere, they normally are not intermittent. I'm more inclined to believe the CCU is the culprit because you've changed to two different Klima's with no benefit. It would be excellent to confirm if the CCU is the culprit before getting a new one.........but, that #10 socket would have to be grounded when the CCU is in economy to positively confirm the CCU.

AlanTbird · #10 03-17-2008, 10:00 AM

All better now!
Found another Klima and while waiting on it decided to swap out the CCU cause the one in there wasnt operationg perfectly...(center flaps had a mind of thier own)
So ofcourse the day after I did the swap with no result~~~the NEW new KLIMA shows up and did the trick.! I wonder if it effects the heater pump also cause that's always been a little wierd.