Benz1978

Replaced ac compressor 3 months ago, Ac turns on when it wants too. Low pressure line gets hot, up towards 200lbs . When it works and cold air comes out it’s low pressure 40-50lbs, this morning ac worked great to work, driving home hot air comes out. After fan high speed click on. Believe ac turned on and cod air came out. Been told it’s the high pressure switch. Within a year I’ve replaced 3 ac compressors, my question is do I have to drain ac system, to replaced high pressure switch or high pressure switch just needs to be remove and replace with draining Freon. 2013 GL450 x166
its a after market ac compressor
dryer has been replaced with new one. Mechanic shop drained and added Freon.

arsupisemnet

You don't replace compressor, unless you don't know what you doing, or whoever does it don't know what his doing.
You start with valve on compressor side. Yes, to replace it you need to drain system. Chinese replacement from Amazon works fine. Just make sure it has build in diode