1991 W126 - Cold Feet

[S-Class Guru]

It got cold today in Dallas.
Went for a ride and got cold feet.
Seems the hot air is coming out the defrost and the side vents, but wouldn't
come out the lower, foot vents.
Everything else is working good, temp regulation, fan speed, etc.

We stopped in the parking lot, and I tried turning the temp all the way up.
The defrost vents howled, then suddenly it switched to the foot vents and all was good. We went into the store, came out, and the foot vents were still working. Then, after we drove about 100 yards, here comes the defroster again, and no foot heat.

So, I assume I've got an intermittant - Lovely!

I'm gonna look at:
1. all the vacuum dashpots, particularly the foot actuator.
(overall vacuum seems good, when I turn on the key in the morning
I can hear the dashpots switch after sitting overnight).
2. Check the foot door for sticking.
3. Check the vacuum switching valve (I replaced it last year I think).
4. Ignore the control head as long as possible - Ha.

Any other suggestions?

Thanks,
DG

[brandlj]

You are on the right track. It sounds like a bad footwell pod. I had one last year. Easy to diagnose with a mityvac.

John 86 300sdl