a/c problem on 1991 500sl


Asked by Jul 04, 2013 at 01:44 AM about the 1994 Mercedes-Benz SL-Class SL500

Question type: Maintenance & Repair

"Hi I have a 500sl 1991 with a a/c problem, the compressor works just above 1000 rpm, if you leave the gas pedal the compressor cuts off and won't work again until you turn off and turn on the engine and maintain the engine above 1000 rpms.I appreciate ..."

5 Answers


Sounds like a sticking pressure switch for the refrigeration system. Have the system checked to insure there's the proper amount of refrigerant in the system. Then test the pressure switch. HTH -Jim

1 out of 1 people think this is helpful.

I replaced compressor, expansion valve, dryer, pressure switch, and check 3 times the amount of Freon, thanks.

1 out of 1 people think this is helpful.

Check your throttle position sensor. At wide open throttle most vehicles will shut down the A/C compressor for additional power. Perhaps the computer "thinks" you've got the accelerator floored and is shutting down the A/C compressor. Another possibility might be a defective A/C compressor clutch. Maybe it's losing it's grip at higher RPMs. One last thought, did you make sure you plugged in the correct plug back onto the compressor? I once had a guy come in with a '72 Coupe deVille. His A/C was doing the same thing as yours. Back in the '70s GM used an emission control device called transmission controlled spark (TCS). It only allowed vacuum advance to the distributor when the transmission shifted into high gear. This was accomplished by using a solenoid which, when de-energized, sent vacuum to the vacuum advance on the distributor. The plug for the A/C compressor and the TCS solenoid were identical. Whomever replaced his A/C compressor (for the record not me) got the plugs mixed up. So whenever the transmission shifted into high gear his A/C compressor shut down. HTH. -Jim


I solve the problem!!!! thanks, the compressor pulley was big at the oe, I know sound crazy. thanks


Awesome! Glad your cool again. BTW that's a new one on me. I never would have thought of that!! Great job!! Thanks for letting us know as well. -Jim

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