I found (and tried) a Bosch 124 830 08 85, but the unit wasn't any good
(controls wouldn't work). I also found a 124 830 21 85, so I picked it up
just in case. The 21 works in my car-- controls and all. Opens the center
vent for A/C but doesn't blow cold air (just heat).

The 124 830 08 85 blows cool air thru the center vents, but the air in the
footwell blows warm. I'm taking the cool air as a good sign and am going to
have the rest of the system checked as I suspect that the A/C problem is
really somewhere else.

An indy says he can change the fittings for a diagnostic without converting
me to R134. That way he can tell whether it's a leak or electrical problem.
He's a Benz guy himself and suggests this as a way to keep the R12 if
possible. I have access to an R12 refill (I assume he's legally certified to use
it)-- now that I think of it-- I need to ask him whether the changed fitting will
still allow for an R12 recharge.

I also found a list of PBU numbers & models at The Benz Store.
The W124 references were:

124 830 08 85--> 1986 300E, 1987 260E & 300E
124 830 18 85--> 1987 300D
124 830 33 85--> 1988-95 260E, 300E, 300CE, 300TE, 300E 2.8, 300E 3.2, E320

It lists the 124 830 33 85 as completely interchangeable with 124 830 (21,
22, 23, 24, 30, 32) 85 although it doesn't say what models those units
originated from.

If anyone's interested, the entire list can be found here:
http://benzstore.com/push_button_operating_units.html

__________________
k. darkman
1987 300D Turbo 200k