First problem for this car
I have owned my 2002 E55 for about 6 years now and no issues at all except to day.Mt AC makes a hissing sound and it goes on and off whenever. AC works but does not blow as cold as it should and hisses loud.
Sounds like a compressor problem or evap leak, or perhaps a problem with the climate control head unit.
Sounds like the AC system is low on gas, there is a valve inside the car that hisses when this happens, Top up and check for leaks i would think
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