1994 E420 A/C problem.....advise needed
 

I bought this car last July. The AC was freshly charged when I bought it and worked fine, but stopped working two weeks later. The MB dealer checked out the system and found nothing wrong; the system started to work again. I drove cross country to AZ, and everything worked well all through the 115 degree summer. I stopped using the AC in fall, but noticed that the system seemed to go on and off once in November when I used the AC (wasn't sure, since it was cool outside anyway). Now the system doesn't work again. I took it to the local dealer, who said I need a new evaporator and expansion valve.

Is there any other switch/control that could explain the AC problem apart from the expensive evaporator repair? I'm not sure this dealer spent any real time diagnosing the problem. I know the last dealer spent a good amount of time checking out the system and found nothing wrong then with the evaporator. Any advise would be greatly appreciated. Thanks.

An evaporator problem doesn't come and go. The problem they have is that they leak.

Find an independent that will do a florescent leak test. Have them find out if the system is low and then refill it and see how long it lasts and then find the leak for sure with a black light.

There are plenty of electrical reasons for the system to not function and then function. Not so with a leak.