I had to replace an o-ring on my ac system (klima sanden conversion kit), when i did I replaced the dryer then vaccumed the system for a few hours and let it sit overnight. no leaks. I added three cans of r12 (system has not been converted) and all was working. According to the factory sticker and the weight on the cans I needed a fourth to get to the 1.3kg. So I added the fourth and drove a bit and all was ok. Today the compressor stopped coming on this afternoon. i hooked my gauges up to it and Im seeing 130 psi on the low side and 110 on the high side. What do you think is wrong, is it overcharged somehow? Ambient temp under the hood must be at least 110F. This is all with the engine off since I cant get the compressor to turn on.

Update: I jumped the compressor on for a few seconds and both the high and the low side equalized at around 50-60 psi. The ac cold nice and cold for those few seconds so i think the compressor is ok. Does this seem like its over or undercharged? Howcan i test to see if the pressure switch is giving a high or low signal? it shows 2 ohms of resistance right now

How hot is it outside? The pressures seem whacked out to me. If it is 90 dF outside and you are at idle you should see 200 to 250 on high side. It should not be that close to equal with compressor running. The low side should be around 35 or so.

Going on memory here so y'all correct me if I'm wrong.

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Jim

its about 85 today, could it be because i only ran the system for about 5-10 seconds? I didnt want to damage the compressor if it was low or high. Not sure if I'm dealing with a charge issue or an electrical problem. it sucks that the factory manuals are not available online easily anymore...

There should be 2 switches - one for the fan and one for the pressure (its 2 function - it will open if the pressure is too low or if the pressure is too high)

The pressure switch is on the "high" side of the ac system and it's either open or closed so don't look at resistance but look at continuity.

If everything is ok it should be closed. If the pressure is too low or too high it should be in the open (no continuity).

110psi the switch should be closed.

It should open if it's below ~30psi and it should also open if it gets above ~300psi

Ok thanks that helps a bit, sounds like the freon charge is not the issue then since the switch has continuity. Jumping it didnt make any difference either.

If the compressor is not coming on then the next thing to check would be the klima relay (ac clutch relay)

You can try and remove it and power the ac clutch directly to check if the clutch works.

The relay is next to the "blue ufo" on a 123 but I could be wrong.

Of course you will need a wiring diagram to know which pin does what.

Ok i forgot that you jumped the compressor already so here's what to do next:

With the klima relay removed check at the plug:

Signals from the pressure switch, evap sensor, ccu and engine overheat sensor (not sure if your car has it)

Then we will be able to say if the relay is faulty

4 cans sounds like too much. I have gotten decent AC with 1 can and plenty of charge w/ 2 cans. If you can no longer source R-12, I have use Duracool in my M-B cars and even my 2002. Works great and fine w/ your mineral oil. I don't fear the absurd web statements about "explosion hazard", perhaps since I did Phd research in combustion.

The AC compressor stopped engaging in my 1985 CA 300D. Culprit was the OVP relay which feeds the EGR box (behind right cabin kick panel). The rpm signal routes thru there, which the Klima relay requires. I just removed the OVP and EGR box and jumpered across its pins to pass the rpm signal on. Search for posts by others w/ photos.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans