I have a similar problem with my 1986 190e 2.3. When the car is started, the A/C is not on. I found that i need to jiggle the key to the A/C going (sometimes I slighty turn the key counter-clockwise, but you can't turn too much as the engine would shut off
) It is a pain in the ass though, and any help on this subject would be appeciated. If it costs a lot of $$$$ to fix, i can live with what i got
Peter