I need help with my trouble shooting on this car. The a/c system works fine for about 3 minutes after I start the car. The the clutch disengages and doesn't re-engage. My first thought was low freon, but it isn't short cycling. But I checked system pressures anyway. On the low pressure side with sytem running and I have right at 28PSI and it is steady from start until the clutch disengages (outside air temp 83* F). It equalizes to 150psi after the clutch disengages. So I beleive that is ok. When the clutch is engaged it blows very cold air.

Next I did the test in the ATC system. The right side displayed the number 1 and the left side displayed 89.

Based on this info, can anyone help me out. Sleepwalker are you out there tonight???
Thanks,
Rick

 

compressor won't work if the pressure is less than 8 bar or more than 20 bar to prevent damage.

check you expansion valve. compressor flupper valves inside must be faulty too.

 

Where is the expansion valve hiding at? Flupper valves, you got me on this one! Is that a repairable thing or does it mean a compressor change out?

I was thinking this was an electrical problem.

So if the system needs at least 8 bars to run, does that mean just to start or is that 8 bars on the low pressure side min. running? That seems like it is very high to have 8 bars (117 PSI) on the suction side of the system running.

 

on the firewall. just beside that brake booster.

sorry, i got it mixed up. 8 bar i mean is the cooling operating pressure. less than 1 bar is the compressor cut-out. thanks for correcting me.

 

Evap temp sensor-- if ac unit doesn't see a logical temperature drop on the evaporator it shuts off the compressor.

 

yes, but he will notice the red LED on EC button on all the time and cannot go off.

 

It won't show red LED , won't set any codes, way to find it is with a resistance measurement or actual values on DAS. I've probably replaced 15 or so of these on both E class and C class with exactly this complaint.

 

well... aarlucas, tell us more about it.

 

Thanks for all the input guys.

Sleepwalker, I was in Florida for a little vacation time!! We drove my truck and left the sick MB in the garage. Anyway,
I checked it out today and the a/c is working fine. I didn't do anything to the car except let it sit in the dark. Who knows. The evap temp senser makes since. Where is that located just in case. I'll just keep my eye on this thing. I'll post the final outcome too.

My check engine light did come on today though. I got the lean, bank one and bank two. I'll tell you, I'm not sure these MB's are all they are made up to be. We've had ours for one year and we are thinking about getting rid of it. Just one problem after another.

 

I took laterthatsamedays advice and changed out the Evap Temp Senser. Now the air blows ice cold again. Thanks Joe!