That makes it even easier...then it is either the radiator or could even be a lazy thermostat or worn water pump impeller.

I agree.

I'm reviving this thread because I had posted the idea of wiring the aux fan to operate any time the compressor was engaged as a way of "fixing" the problem created by a previous owner and was criticized a little about it being a "hack fix".

I was reading on the MBCA site that someone read in the Mercedes Benz Technical Companion that MB recommended replacing the relays in AC systems that had been converted from R12 to R134a so the aux fan would run anytime the compressor ran...that is very interesting and would probably help some people who have marginal cooling with converted systems, especially if they drive in stop and go traffic a lot.

So, maybe my hack fix isn't such a hack after all and would help some with marginal AC performance that had converted systems.

Maybe these systems shouldn't be converted to R-134a. ;)