My wife has a 2000 E320. We had a A/C hose concection leak which I fixed and refilled with R134a. Everything worked fine for a couple of days then the ac started acting up once again. There is no EC light on and the ac seems to work fine in the morning hours or when the car is first started in the morning. If you drive the car to work, cut it off and go back out in ten minutes or so, the ac will not work at that point. I did remove and clean the duovalves this morning to make sure this was not the problem. Everything worked good until she got back into the car a couple of hours later to go to work and no ac. I am sure it is a sensor somewhere, I just don't know where. Any help will be appreciated. Oh yea if I don't get this fixed I'll be the one in HOT water!

 

not much concrete info to go by. try running through this process and see if it helps
isolate things a bit more.

http://www.eclassbenz.com/

 

I'll take a stab at this one...My E320 did the exact same thing. A/C worked fine when first started, then quit as soon as the engine warmed up. You need to stick a set of gauges on it to check the high and low pressure, not sure about MB, most cars are around 50-60lbs onthe low side and 200+ on the high. The fact that your a/c comes on at first indicates you must have sufficient pressure to make the low pressure switch cut the compressor on, so you probably don't have a leak in the system.. My problem was the aux cooling fans. One must be running continuously when the a/c is on or your condenser core will heat up and make the a/c get hot.

Disconnect the leads to your fans and put 12v to them individually to see if they are working. If they both work straightwired, then see if one comes on with the a/c and the other after the car sits idling long enough for the other fan to come on. If the fans work hotwired but not with the sensors, you have bad sensors.

I replaced the fans and cured the problem. Unfortunately this is not as simple an operation as it was in my old 123 diesel. I had to remove the radiator to access the fans. The fans aren't cheap (almost $300). I removed the pair and discovered they both were gummed up with pine needles and dirt. Cleaned them out and got one working. i tried to get out cheap, so I put one new and one old one back in and it worked for about a month before I had to take the whole blasted thing back apart to replace the other old fan. Lesson is, if they both look gummed up, replace the pair so you don't have to tear the radiator back out again. hope this helps.

 

I may have similar problem. Last year my a/c had two problems. Blower air was too weak and then the cold air will stop on a hot day (86 degrees ambient) driving 30-40 miles at freeway speed. (The a/c clutch was tuning off) I fixed the first problem by replacing the blower motor regulator BUT the second problem is still there.
There is no problem with local driving.
The diagnostics I have done is that when a/c is ON, both fans in front of radiator are ON. HOOD is open. Both fans cycle continuously with ON time of about 1 min. and OFF time of about 15 sec. This was done obviously when engine was idling.

Then I closed the hood. The a/c was still working but the fans are continously running now. The whole test took about 20 min. and the a/c did not stop working.

Does the above test make any sense ? Please tell me what more can I do.

 

My a/c quit in my e320 1999, we have recharge the freon, checked for leaks (none) checked fuses. Tried moving relays still just the ec works oh, and heat works. Where would I find the regulator that could be bad? And is there something else I can try?