In honor of $1.70/gallon gasoline, I've resolved to bring "Ms Hades," my '78 300D back from retirement. She has only 97k, drives and runs well, but is constantly in need of multiple repairs.
The list is too long for this post, but since it's summer in Fla, the control of climate has finally reached the top of the list.
4 or 5 years ago, the climate control servo was replaced, curing intermittant pushbutton operation.
Alas, the car sat for a few years, as the repair list again lengthened, although the a/c was fine. Now that she's back on the road again, after a few weeks of normal a/c operation, things have gone to "hell" again, so to speak.

Now, although the compressor turns, and the system cools, suddenly only hot (hot!!) air issues from the left,right,and floor vents.

I've ordered the MB shop manual cd, since Clymers and Chiltons are worthless for diagnosing a/c systems. I hope, when it arrives, I'll be privy to some of the deeper mysteries of Benz repair. Meanwhile, I sure could use some advice on diagnosing this problem!
How is the beloved climate control servo tested? I know I have hot water going to the heater core, since the hoses at the firewall are hot. I've checked/exchanged fuses (although the schematic diagram in Clymers show an in-line fuse going to the climate amplifier,I haven't been able to find it...), but beyond that I don't know where else to begin: eg expected voltages at the servo, how to check the pushbutton assy, vacuum vent doors, etc.
Any suggestions will be very gratefully accepted.
Now, off to hunt down door stoppers, turn signal/hazard switches, doorlock selenoids, seat cover, and whatever falls off this week.
jeeze, I love this car (BG)
ac

------------------
97K '78 300D