I am at work.
I will try it later this evening.
But was wondering is the pig tail coming of the drier the temperature sensor or pressure sensor? Is there a low and high pressure sensor on the drier? Which one is the low pressure sensor?
A

__________________
1987 300SDL
187,000 miles

I think Brian mentioned that it is the lower one. The other one is a valve I think. Just take the wires off and connect then together. Then start the car and turn on the AC. If the compressor comes on then the low pressure switch is bad, or it is good but you do not have enough pressure in the system.

__________________
Doug

1987 300TD x 3
2005 E320CDI

My AC is R134.
I think the switch is high and low?
Will this test still work Brian?
A

__________________
1987 300SDL
187,000 miles

Just jump the leads to the lower switch on the dryer.............the upper switch is for the auxiliary fan..........you can jump that too...........and see if your fan works...........

Pull the two leads off the switch on the drier and "jump" them together so the switch is out of the circuit.Check for continuity between the CCU (#7 socket) and the Klima (#10 socket). ----Got Continuity, getting somewhere now---

If you have continuity, then put the CCU back in place and test for ground at #10 with the a/c selected. If you get a ground, the CCU is good and the system is low on Freon or the switch on the drier is bad.
----@$%#! Wide open----
Does that mean my rebuilt CCU is bad?
Put the previous CCU on and same result......
I did try something though...
Previously, if I jumped #5 and #7?
I cold get the compressor to run and
I have cold air. Not now.
Is there a way for me to test the
compressor?
I know its an old car. I enjoy working on
it. But man, I would like to win every
once in a while to make the effort worth it.
What's the next move gents?
A

__________________
1987 300SDL
187,000 miles

If you have continuity with the drier switch jumped but cannot get a proper ground signal at socket #10 with the a/c selected (any of the left three buttons) then the CCU is NG.

Be sure that you are measuring continuity to ground when you make this test. In fact, the book recommends you measure voltage: One lead in socket #10 and one lead in socket #5. If you measure battery voltage, then you are getting the ground on socket #10. Sometimes this is an easier test..........less likely for operator error.

If you can't start the compressor by jumping #5 and #7, you better see if you still have voltage on #5. Was the keyswitch in the #2 position for all of these tests with the CCU in place? You'll never get anything without power to the CCU.........and you only get it with the keyswitch in #2.

Riethoven,
I did not turn the car on....
Will that matter?
A

__________________
1987 300SDL
187,000 miles

I am referring to the socket(5+7) for the Klima relay in the previous post.

__________________
1987 300SDL
187,000 miles

When I was jumping 5 and 7 the AC was on and the car was running and no AC......
But it worked before, I will put my old CCU in and see if jumping these 2 sockets activate the compressor. If it does not, does that lean more toward the compressor being bad.
A

__________________
1987 300SDL
187,000 miles

When you jump 5 and 7 at the Klima, the CCU is not in the equation. You've pulled the Klima and there is, by definition, no signal from the CCU to the compressor.........because the Klima is not present.

The only signal from the CCU to the compressor is via socket 10 which signals the Klima to start the compressor if all other parameters are within an acceptable range.

If the compressor won't engage with the sockets jumped, you might have a wiring problem. Check for continuity between socket 7 and the compressor. Intermittent issues are wiring.........not usually the component.

Brian,
How do I:
Check for continuity between socket 7 and the compressor?
Thanks
A

__________________
1987 300SDL
187,000 miles

There's a plug at the compressor. One of the sockets must have continuity with socket 7. If the plug is corroded internally, you found your problem.

Brian,
Is that continuity between socket #7 of the Klima, or #7 of the CCU?
Thanks
A

__________________
1987 300SDL
187,000 miles

"In fact, the book recommends you measure voltage: One lead in socket #10 and one lead in socket #5. If you measure battery voltage, then you are getting the ground on socket #10. Sometimes this is an easier test..........less likely for operator error."
There is voltage. What range of voltage am I looking for?
I see a set of wires coming off the back of the compressor and they lead to the front. Very tight fit to get hands on the sockets. To take them off. do they pull up or to the back of the car?
This is the first time I actually had the ac on an extended period. Air coming out of the vents were not hot(but not cold either. Could I have a leak. I did convert it to R134a. Do you think it would be worth to by one of those refill stop leak kits that have a pressure gauge on it? Do you know how much pressure there should be? Or is it different for R12 and R134a?
Thank you.
A

__________________
1987 300SDL
187,000 miles

If you have 12V between socket #5 and socket #10, the CCU is doing the proper job.

If the compressor is now working, why are you bothering with the wires and the plug at the compressor?

If the compressor functions and the air at the vents is not cold, it's time to put a set of gauges on it. Nobody can tell you what's wrong with it without some gauge readings.

No, you can't use one of those refill stop leak POS devices..........unless you get extraordinarily lucky. If you don't and you ruin the compressor, then you get what you deserve.