Thought I would post here too -a/c prob
 

It's getting hot, a/c not working - posted in sl

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Hi everyone! I have a 1986 560sl and recently was told the compressor was no good since my car was not blowing cold air. Air was coming out but not cold. Ok, so had the compressor replaced along with everything else that goes with it. Still no cold air. The compressor would not kick in, so bought a new relay switch since we saw the old one was burnt. That had not corrected the problem. Saw the switch on the dryer (thermostat switch, I think) had to be grounded to kick on the compressor (if I got that right). Any suggestions? It is getting hot already here in Texas. There is no power to the compressor and also the dash lights are dim, could there be a connection?

Thank you kindly!

I will throw some darts. Voltage regulator/alternator CAN cause dash lights to dim, but the dimmer on those old clusters are also notorious for failing. Bummer on the AC, did you check you AC relay? It sounds like you are addressing most of the components, the relay was the only thing I didnt see you mention.

As always, clean and re-secure all grounding straps,wires,cables, etc. More than likely not the problem but you have to have a good basic full electrical circuit to begin with. Relays are sensitive to a less than optimal circuit.

Here are the climate control electrical diagrams for 86 and on...
http://www.startekinfo.com/StarTek/outside/12253/program/ETM/ACCfrom86.pdf

Note in general for all vehicles (not just Mercedes), the refrigerant pressure in the A/C lines needs to be a certain pressure, but not too much pressure before the compressor will be allowed to come on.

So one of the first things I would check is the A/C refrigerant pressure and associated pressure switches.