Eratic A/C performance in 95 C280
 

The climate control in my 95 C280 is behaving very eratically. It cools just fine most of the time.(Until recently I've noticed some vents blowing cool and some blowing warm) Primarily the fan blows at full blast when there is no load on the engine (idle or decelerating) then calms down when I resume speed and behaves better but still not perfectly as it did last summer. I suspect a vacuum leak but that's only pure speculation on my part.

That is most likely the problem. A vacuum leak will be pretty hard to check by yourself. You will probably have to remove the whole dash to replace the vacuum servos that have failed.