I have a 2005 NA. Recently I had my ac clutch go out so I ordered and replaced the compressor, expansion valve and the condensor.. The ac work fine after I flushed the lines, vaccumed out the systen and recharged it. However, a few weeks later the new compressor blew its seal. (SOUNDED LIKE A GUN SHOT) Thinking that I had puechased a bad unit, I ordered another from someone else.. I again installed the new compressor and evacuated the system again. After charging the system back to factory settings the ac worked while the car was idling in the drive.. Once I got it on the road, the new ac, which has a high pressure relief valve, blew the valve and I lost pressure on it again. I took the car to several mechanics, one whe even specialized on ac's and they can't figure out why the pressure keeps building when drivibg the car. The Benz dealer claimwd they did not have the tools yo even diagnose it. The only thing that I have noticed recently is the cooling fan is NOT going to high when the ac engages.. When it did work properly, it sounded like a small plane was about to take off from under my hood...

I need help please... No one around is familar with the car and like me, is just guessing as to what the problem might be....

Sweating in Arizona, Dale...

 

First normally just the LO fan is on with the AC mainly for air flow through the condenser and not for engine cooling. If not on at all (RCM) then when stopped pressures are liable to go sky high and pop the blowoff.
Second otherwise your problem sounds like a blocked high pressure line, as part of your repair process did you blow the lines, condenser and evaporator out ? Particularly after "new compressor blew its seal". For either I doubt that a scan tool is going to help you.

ps there is nothing unusual about the AC itself, find a better shop. Are you anywhere near ACKITS ? 7904 E Chaparral Rd #A110-608
Scottsdale, AZ 85250 602-233-0090

 

"First normally just the LO fan is on with the AC mainly for air flow through the condenser and not for engine cooling." However when the ac was working, before the clutch went out requiring me to replace it, the fan would ALWAYS run at a higher rpm forcing more air over the condenser when the ac would engage. Now however, it only turns on now and then and NEVER at the higher rpm you would expect when the AC is under a load!

 

And yes, that lines and the condenser were cleaned and evacuated and vacuumed down before charging the R134..