As its been real hot here in NYC the AC on my 2000 C280 (240,000.00 Miles) has quit on me. Hooked up guages to read the high and low side of the system as the compressor is turning just no cold air. The readings are

Low Side = 45 PSI
High Side = 115 PSI (seems low)
Ambient Temp 91 deg

Can some one please point me in a direction here as I dont want to change parts willy nilly. Does the above indicate a compressor problem or a blockage?

Money is always an issue? MB wants to charge over 3 k to repair. I need to offset some of this cost. If I need to replace parts I can do this and leave the flushing and vacuming to a service shop.


Thanks in Advance

Rob

High pressure too low....start with evacuation..pull vacuum..add oil & re-charge system...the compressor is of a variable design..if the expansion valve doesn't ask for higher quantity then the compressor will go into a lower output stage..

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i have seen same deal twice in last two weeks in dallas.valves in compressor have failed.replace compressor and drier,flush system,evac and recharge and you will be as good as new.david poole european performance dallas tx.

Where is the low pressure connection to check AC pressure on a 1994 C280. I looked everywhere and can't seem to find it. HELP please.

Thanks to all that replied. I am amazed that I actually got this thing to work. I took the path of least depleation to my wallet and followed MB DOCs post. The system no reads 250 - 300 lbs on the high side. The vent temp has gotten down to 43 degrees. This is the best that the system has worked for 2 years. I dont think that it is 100% but after 245K what is. I'm satisfied for now. Once again thanks. One question with this being a variable design how do you know the correct amount of 134 to put in. The specs call for 20 some thing ounces I think. Is there an optimal reading or is the bench mark approx 40lbs low 225-250 lbs high?

Baggyboo - I had to search for a min to find my high side port also. If yours is like the 2000 setup the high port is in the front next to the radiator on the drivers side. The cap was black so not readily noticed. this is facing out to the street not in to the engine compartment.


thx

Rob

Hi Robert.

Thank you for your reply, I'm actually looking for the LOW pressure side on a 1994 C280. I'm trying to add r134a. I can not find it and it is driving me crazy. I went to Autozone yesterday and the guy could not find it either !!

Many Thanks,

oops sorry about that. Reading is fundamental right. I automatically assumend that it was the high side you were looking for because I couldn't find it on mine. I am not familuar with the 94. did they use 134A back then? I thought it was 95 for the change from 12 to 134.
Maybe you can trace the connections from the compressor or the evaporator to locate the valve. Sorry I am not any help here. Good luck though.

Thx

Rob

The air conditioing low pressure side on a 1994 C280 is on the driver side, at the bottom, up front near the headlight !!

Glad you found it. Sounds like the same place my high pressure port is.

Great day here to test the AC - 115 deg. heat index.

Rob