I am interested in hearing what the noise sounds like too!
My 85 300SD is making a very loud piercing wine/hiss noise when the compressor is turned off. Like it's releasing a lot of pressure. Any thoughts of what that could be?
Also my A/C has been converted to R134 a long time ago. The A/C only works well(somewhat) if the car is steadly moving at a good rate of speed. But when you stop at a stoplight or in stop/go traffic it starts to blow out hot air? Any ideas would be greatly appreciated.
Didn't mean to highjack the thread!

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1985 Mercedes Benz 300SD, TMU
2015 Chrysler 200S