190D vacuum pods all the same?

[Jetmugg]

I'm having an issue with the heater on my '84 190D. One of my vacuum pods isn't holding vacuum, causing me to lose my hot air at times. (It's cold here right now). I think there are 3 vacuum pods in the dash. The other 2 hold vacuum and seem to function properly.

My question is whether or not the pods are all the same, or if each one is different from the others. I might do a "quick swap" to restore my heater function for now, until I can get a replacement pod.

Thanks for any help you might be able to provide.

SteveM.

[JimSmith]

I suggest you call Phil at FastLane and ask him. I did not see the pods in the list of parts in their on-line catalog, but it seems to me a vacuum pod can't cost so much as to be worth the work you are describing to replace the unit twice. Jim

[sixto]

The pods direct where air goes, they don't determine air temperature. On other MBs temperature problems usually trace to the monovalve. I don't know if a 190 has a monovalve or another kind of heat controller. If you're saying that you're not getting hot air where you need it then look to the pods.

Sixto
93 300SD

[Jetmugg]

No "monovalves" on the 190s (Thankfully). The heater core gets hot, but instead of heated air, it appears that I am getting "vent" air out of the heater ducts. I hooked my mityvac up to all of the vacuum pods (one at a time). When I got to the one that wouldn't hold vacuum, if I pump the mityvac, then I get hot air. I have looked it up, and it seems that this is the pod for the "main air flap", that determines whether outside vent air goes to the cabin, or air heated by the heater core.

SteveM.

[sixto]

Looking at the EPC I see 4 vacuum pods:

One is way high on the air box p/n 201 800 08 75 with no functional description although it appears to be near the air mixing flap control resistor.

One is right on the driver side of the air box p/n 201 800 05 75 (or 000 800 87 75 from VIN F 002651) for defroster flap control.

One looks to be deep in the driver footwell p/n 201 800 03 75 for footwell flap control.

One is somewhere on the driver side p/n 201 800 00 75 called main air flap control.

Seeing as non have the same part number I'd say they're not interchangeable.

Sixto
93 300SD

[sixto]

Typically outside or recirculated air is a separate function from heater core or evaporator. The default for a bad pod is to flow air over the heater core. Getting outside air to the footwell without going through the heater core seems impossible based on the architechture of other MBs. Maybe it's so cold where you are that the heater core can't warm outside air enough.

Some places now sell replacement diaphragms for these pods. The replacement diaphragms work passably on single function pods; not so well on double function pods. Remember that those pods are over 20 years old and very brittle so use light even pressure if you decide to take one apart.

Anyway, I hope you get heat soon.

Sixto
93 300SD

[Jetmugg]

Sixto:
Thanks for the info. on the part numbers. The correct one is $60 through fastlane.
I have heat now, but I have to leave my Mityvac hooked up to the vac pod, and give it a few pumps if the flaps fall closed. With the flap opened properly, the heater blows nice and hot.

SteveM.