OK so I have read as much as possible here and elsewhere about trying get a handle on this. This is a 1983 300d. Here what I see and what I think:

Problems / what I see:

1) Compressor not engaging, can be made to do so by jumping wires on top of evaporator.

2) With compressor engaged 0 psi on both high and low side. added 1 can refrigerant with compressor jumped and running still 0 psi both sides compressor doesn't engage without jumpers.

3) center vents not blowing anything.

4) Fan blower motor starts and stops when I ask it to. Haven't checked heat.


Here's what I think:

Next test would be to take care to A/C shop and ask for Vacuum test?

If vacuum test doesn't show leaks then:

1)compressor may be bad even though is spins freely.

2) next steps would seem to be replace or rebuild compressor, evaporator and expansion valve.

3) Center vents unrelated vacuum system problem separate diagnosis and repair.

4) can't evaluate ACC until rest of system check out ok.

Does this seem like prudent course of action?

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1972 280SE 4.5

Sounds like you have a major leak. Even without the compressor running you should have pressure as long as there is any liquid freon at all in the system. The pressure is temperature dependent but would be in the 80 to 100 psi range when the compressor is not running (the system stabilizes and the low and high side will have the same pressure.

You should be able to tell where it is leaking by adding freon without the engine running and listen for the leak.