Eliminating High / low pressure swich '87 560SL
 

Hello
The AC compressor on my '87 560 SL is not engaging. I have checked the fuse and replaced the compressor relay. Next, I believe I need to check the High/Low pressure switch on the dryer. To test this, can one simply bridge the wires on the switch? Any advice would help.
Thanks

You COULD bridge the low pressure switch, but the switch is there for a reason - to protect the compressor. I've done this for another reason-to keep the fan engaged at low speeds at all times in the summer (but I KNOW I need freon and NEVER operate the A/C, I leave it off or in economy at all times).

You know as fact that you have proper amount of refridgerant installed?

You can jump it for a second or two to test it. It is jumped when you have to add freon to a system that does not have enough pressure to close the switch.

BTW - are you testing the compressor on DEF? That setting hard-wires the connection to the compressor. Other settings rely on vacuum switches in the ACC system and those are usually the problem.

Still trying to get the compressor to start !
 

Thanks Strife and CTaylor. I have the setting on Defrost but still no luck (the fan does blow in the cabin though).
When I jump the High Low presssure switch, the aux cooling fan for the engine runs, but the compressor still does not start....
I dont know if the right amount of freon gas is in the system....is it freon (r12) that I would need to charge a stock '87 roadster with do you know ?
Any further advice would be appreciated.