gentlemen,
love this forum, lots of good practical info. thank you.
concerning an '82 300td, w/ fresh ac recharge, i count 5 vacuum operated doors; all working properly, electric water valve; working,
here's my question: why does my ac work fine until the climate control shuts it down. once it shuts down, it just gets warmer and warmer. the condensor (isn't that what they call the thing in the heater box that gets cold?) is still extremelly cold. is there another door that i can't find or does the air run through the heater core and condensor all the time?
thank you, db (ben's dad)

I don't think there are any simple ac questions myself...

The thing inside the box is the evaporator... where liquid refrigerant is let out in a spray and changes to vapor... adsorbing heat.... thus cooling fins...

It sounds like maybe the sensor on the dash,,,if you have one,,, might be dirty... and thus not responding quickly enough...

There are other things which can be going on ...so you may have to do more describing for us to be able to narrow it down...

The problem may very well be that the foam hose behind the glove box that draws air across the temp sensor in the middle of the dash has disintegrated. Pull the glove box and look. If it is gone, get a section of foam hose from home depot. It is what is used to insulate pipes in the winter time.

Good luck,

evaporator? cool!!, hose was replaced, i observed that my heat never really stops even with it off or in economy, maybe that electric valve isn't as good as i thought?

Or maybe the vacuum regulated flap which is supposed to change your airflow from heater core to evaporator core is defective ?

Sounds like the mono valve is a problem. Get a rebuild kit and replace it.

dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

dmorrison is right here. It sounds like your monovalve diaphragm is torn/leaking. It's a common occurance and is inexpensive to fix. Just go to Fastlane at the top of the page and Phil can hook you up.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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leathermang,
that's what i thought but i don't see one that would perform that function. where would it be. i found 5; 1) defroster 2) floor heater 3) center dash vents and 4&5) above the fan regulating the "source" air. there is a red and black vac line that goes over the heater box to the back side, can't find the end, maybe it goes to another vac motor. if it does, i'll have to pull everything apart to get to it!!!!!!
db

Your monovalve diaphragm is torn. It's an easy, inexpensive fix.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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I don't know if your car has one.... but others have described that as a problem on their cars...
On the other hand.... if it is contained in a "tube" or container fed by only one fan then it might be hard to find .
But it sounds like these guys are sure it is the monovalve...

guess i'll swap the mono valve out w/ my kids car to see what happens.

"guess i'll swap the mono valve out w/ my kids car to see what happens."

Then when they experience those symptoms you can look like an expert telling them they need to fix their monovalve..... LOLOLOL

i exchanged mono valves w/ my kids, mine works now his won't....LOLOLO

That is Classic !

I have a similar problem, just charged my ac and it is barley even cool, i think the compressor is on its way out aswell.

i believe my mono valve has been bad for a long time, i thought a symptom of a bad mono valve was the heater working until you get up to speed and then wont work again until the car is shutdown.

I was unaware it would affect the A/C cooling.

But my vacume pump that controls the doors behind glove box is dead, would this affect cooling?