For those just joining, I've got an 86 560SEL with a CCU in need of some help. That's for sure, because I was able to try a good one. I swapped in a good CCU which by the way has a completely different looking board (this one's from an 88 300E) and the blower works on high and low, but air is not cold, though the AC line running along the drivers side of engine bay is cold. This CCU does run cold air in the 88 300E. So something on my CCU board that has to do with offering high-speed fan is kaput.

1. What on the main board controls the fan?

2. What else may be wrong with this car that is keeping cold air from being offered from the vents?

Gurus, shotgun solutionists, hacks,
I offer myself (along with my problems)
For your perusal,
Thanks,
Mark