Hi I know this is an old thread but I’m writing this to hopefully help out some one who has replaced their ac compressor and you’re getting a 9006 fault code short to earth compressor.
I own a 2006 ml350 w164 and purchased a aftermarket A-Premium brand ac compressor and yes it was a made in China unit. After installing I got a 9006 code which would not clear, the problem was that inside the new compressor on the control valve there needed to be a diode just like the oem denso unit ,unfortunately my unit didn’t have it hence the fault. To correct this I spent $1.25 and purchased a diode part number 1N4007 and soldered it to the wire which plugs into the compressor and grounded the diodes negative end to a rocker cover bolt to earth it out. It now works as it should with no fault code, hopefully this will help.