W202 C280 A/C question - PeachParts Mercedes-Benz Forum

GregZ · #1 04-22-2008, 10:25 PM

Hi All,

My A/C quit working today - the compressor clutch does not engage (not even for a second). Static pressures are fine. I'd like to see if the two pressure and the temperature sensors on the dryer work. In addition I'd like to know if the other pressure switch works. Does someone know what I should be measuring on them so I know they are working?

I was able to put the climate control into diagnostic mode and got code 7 (refrigerant pressure) at 6.1bar=88.5PSI and code 8 (refrigerant temperature) at 82F. Both these seem to be valid (ambient was around 82F). Does this mean that the temperature sensor inside the dryer and the hidden pressure sensor are working? If so, does the pressure switch on the dryer open or close if the pressure is too low (what is normal operation)?

Thanks,

Greg

mbdoc · #2 04-23-2008, 09:04 AM

IS the "EC" light on all of the time?

What is the reading for #5, the evaporator temp sensor?

GregZ · #3 04-23-2008, 09:21 AM

#5 was around 82F, EC is not on.

GregZ · #4 04-23-2008, 10:08 AM

I disconnected the compressor clutch cable, and I see the battery on the cable. Connected it to an old compressor and the clutch engages on that. It seems that the clutch on the compressor crapped out.

mbdoc · #5 04-23-2008, 10:46 AM

Clutch has fusible link to protect the controller from a short.

GregZ · #6 04-23-2008, 10:52 AM

Thanks, but the voltage does get to the compressor except it does not engage.

TimFreeh · #7 04-23-2008, 11:23 AM

Quote:

Originally Posted by GregZ

Thanks, but the voltage does get to the compressor except it does not engage.

IIRC the fuseable link is inside the clutch.

GregZ · #8 04-23-2008, 11:25 AM

I removed the solenoid from my old compressor and indeed see the fusible link on it. I have not taken the new compressor's clutch off yet (as it is still under warranty), but probably that fuse is blown. Why isn't the fuse inline at the connector, seriously?

TimFreeh · #9 04-23-2008, 02:55 PM

Quote:

Originally Posted by GregZ

Why isn't the fuse inline at the connector, seriously?

The fuse in the solenoid is a "thermal fuse" - if the compressor begins to lock up the clutch will slip, which will cause it to heat up. The heat melts the fuseable link and the clutch disengages - I don't think this fuse was designed to be a traditional current protection fuse.

GregZ · #10 04-23-2008, 03:25 PM

That'd make sense.

crashone · #11 04-23-2008, 11:13 PM

Does a 1994 c280 A/C system have this fusable link? If so where can I find a schematic so I can locate it? Or can someone give realativly good directions on how to locate and replace? Which brings up another question----where do you get a new fuse? Dealer? Thank you for the help!!

mbdoc · #12 04-24-2008, 08:01 AM

on 1996 & later a/c compressors the fusible link is part of the clutch.

The earlier cars don't have that feature

crashone · #13 04-24-2008, 09:58 PM

Well.....I was hoping. I'll take it to a friend's shop and see what's up.