A/c not working '07 ml320 cdi
 

Summer weather - a/c blowing warm air only. Replaced compressor and low pressure switch - still not working. My mechanic can start the compressor with his Snap-On diagnostic tool, and it will after that run on its own for a while, blows cold air, then the compressor is no longer commanded by the climate control unit and it's back to warm air again.

Anyone out there know what might be wrong - why the climate control unit won't trigger the compressor?

All fuses fine.

Thanks!!

Dave

I have the same scenario with my E320, 2002 unit. The AC unit is fully charged, no leaks, all fuses are fine, The climate control will not trigger the compressor. Have you had any luck with a solution? My mechanic said the low-pressure valves rarely ever go bad(not a MB mechanic though)
Any ideas would be appreciated.
Thanks,
Guy

Hello and welcome to the forum, below is some info that I was able to find. Hope that it helps you a bit.


It’s most likely a fault in the dampers that control the air path into the cabin if it’s truly “hot”, meaning significantly warmer than ambient. If it’s a newer Benz, find someone that can pull the settings from the onboard computer. I’ll bet you’ll find one of the controls is ‘out of range’ meaning the computer can’t verify the position of the damper.

Of course, the computer could be mucked up, too.

The fix can be as easy as simply dislodging a stuck damper all the way up to replacing the air conditioning controls.

If the air is just ‘not cold’, then you probably have a leak in your A/C refrigerant and that can be a fairly substantial failure of the system as a whole depending upon what failed and when.

Do a search for "AAC burnt circuit W163 no AC"