Q: Need to know the A/C relay location on a 1982 European Mercedes-Benz 280sl.

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When I connect A/c compressor wire to 12v, A/C blows cold and A/C switch lights up. Without the 12 volt jumper, the A/C switch does not light up, and I get no 12 volts to the compressor clutch. Also, there is a dial under the dash near passsenger side of center console. What is this dial for? Does this car have a pressure switch for the A/C? maybe that is why it is not coming on? needs more freon? Where is the relay for the A/C locaated?

thank you

My car has 109000 miles.
My car has a manual transmission.

The relay is on the driver side right next to the brake booster and master cylinder. It looks like a large black block by the fender. For the compressor to not have power to it, check the low pressure switch with the switch on and see if there is power to it. If there is power to the switch, then take a wire and bride the contact on the harness and see if the compressor clutch engages. If the clutch engages, then the low pressure switch has failed. If the clutch does not engage, then the relay is not working. If there is no power to the switch, then the relay is not working. If you need further assistance with air conditioning system, then seek out a professional, such as one from Your Mechanic, to help you.

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