1994 Mercedes Benz E420 AC Intermittent

Is it the fan that stops or does it start blowing warm air?

The blower remains in it's last selected position the compressor shuts down and the system blows warm air.

It sounds like the cycle switch may be bad. THat is where I would start.

What and where is the cycle switch?

THe cycle switch determines how often and when the compressor will engage. Honestly, at this point, I really feel a tech needs to look at it.

My e420 had the SAME EXACT problem it's like you were discribing my cars issue. I took the A/C condenser fan shroud off and found 3-4 inches of dirt packed into the condenser and between the condeser and the fan shroud. First I used a shop vac to suck the dirt out(you dont want to push the dirt further into the condenser) then i used a hose to rinse it off. Be carefull not to bend the fins on the condenser. When I did this it was a conplete difference, it works great now. In the first pic you can see what parts I had to remove. You can also see a small amount of the dirt that had fallen out and onto the ground and the plastic under skirt. The second one you can see the cleaned condenser with water driping off. Total of things to remove: Clips from top of Radiator, Clips from top of A/C condenser, Horns, body colored support beam in front of the condenser, front bumper, front of plastic underskirt, 2 Bolt's that hold the coil loop in front of the A/C condenser, condenser fan shroud(Difficult), condenser fan. If you do all this I sure hope it fixes your problem. Because it's a real task. It's important to note that the dirt was packed in th bottom and was not visible until the fan shroud was off.