My defrost is wide open with the AC on on my 1987 W124 300D. I assumed that the pod was bad and ordered a new one. I replaced it this morning, but it still wont shut. it seems like there is no vacuum at the 7 way manifold? All of the other pods work properly and the AC works as it should. The only other thing that may be related is the shifting 1-2 and 2-3 is noticeably harder in the past week or two, but that maybe a different issue.

Any ideas? How do you test the 7-way manifold?

Thanks,

Geoff

The solder connections in the manifold valve crack where the coils are connected to the printed circuit board. Earlier ones like yours are sonic welded together and therefore difficult to disassemble although not impossible (I did 2 of them). Later ones were screwed together making repairs easy. There is also a foam filter that will disintegrate when you take it apart.

There are 2 valves that control the defrost pod. Pin 5 defroster nozzle flaps, large lift and pin 7 defroster nozzle flaps, small lift. Valves are activated by grounding through the push button unit. Pin 8 is common to all valves and goes to +12 volts fuse 7.

Here are the innards:

Attached Thumbnails

   

thanks, I will test the solenoids first and move on from there.