I'm trying to convert my 350SDL to R134A ( I know everyone says 134a isn't effective, but where I live, it doesn't often get hot enough to really matter. I've had plenty of luck with 134a-converted systems before )

I vacuumed the system down for a good while, replaced the receiver drier, vacuumed it down some more. No leaks under vac so I decided to fill with oil and give it a go.

This is when I noticed that the compressor is stuck ON. Constantly, regardless of the position of the controls inside, the compressor clutch is engaged. Now, there was plenty of oil in the system when I drained it, but I have no idea how long the compressor has been stuck on for.

The only time the compressor clutch will disengage is if I disconnect the Klima relay.

Regardless of the compressor being stuck on, it won't take any refrigerant at all and won't blow cold air.

I've never seen a compressor stuck on and don't know what would cause this or what the consequences are: bad Klima relay which trashed my compressor, perhaps? Insights appreciated. My friend is going to have me swap relays with him, we'll see if that lets the compressor finally turn off, but I still don't know if it's now burnt up or not.

How about if you disconnect the low pressure switch at the receiver/dryer?

Sixto
87 300D

Disconnecting the switch does absolutely nothing; compressor continues to run.

Removing fuse 5 turns it off.

It's possible to have one of the relays inside Klima stick and stay on all the time (the more usual problem is that the failure won't allow the compressor to engage). You can remove Klima from its case and check the relays for burned contacts. Swapping in a good Klima would be quicker.

Klima has a number of inputs that all must be "good" for the a/c compressor's clutch to get power. Usually the problem is with one of those inputs. We know the clutch is good since you can force it to disengage by removing Klima. IMO, one failed-on input would not make Klima stick. However, one experiment would be to turn the ACC off by pressing the right hand button in the row of 5. If something is wrong with ACC it could be forcing Klima, and therefore the compressor, to be on most of the time. A related experiment would be to unplug the two cable from the ACC unit.

I don't know if there is a component (e.g., a transistor) that would fail in such a manner as to keep the relay on all the time but anything is possible. Unless you are up to doing surgery on such a device, you would have to replace Klima. Note that Klima tends to be very model-specific: you can't swap in one from a gasser, for example, and expect it to work correctly. That makes shopping for a used one more challenging and new ones are expensive.

Jeremy

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Consider and ice cube relay while you're waiting for a suitable Klima relay. You'll be without the protective interrupts but it doesn't seem like the forum is awash with compressors and engines that blew up because the Klima relay wasn't there to protect them.

Sixto
87 300D

Thanks guys. The ac has actually charged up to work well- just took FOREVER for it to accept the charge but it's cooling well in 90 F with sun.

I'll swap the klima with my friends tonight... If that solves it, I'll bypass with the ice cube relay. Not sure how to do that but I'm assuming it'll pop up in a search.

Swapping klimas fixed the issue.

I swapped in an ice cube relay for simplicity's sake. As a British car owner I hate complex electronics.

As a British car owner you probably hate all electronics

Sixto
87 300D

I almost asked where in Central Ohio you were.


Sixto, this car is running your ice-cube relay conversion now.


So others can find it,

Anybody have this part? 003 545 6905

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