126 Climate Control

[fintail]

OK, first off I know there are many threads about 126 climate control issues. I did read through them, but I can't find one with a problem exactly like mine.

Like in many threads I read, the heat in my 126 (300SE 1989) doesn't work correctly. I get warm (not hot) air out of the side vents, but cold/ambient air from the center vents, no matter the temp. wheel position. All fan speed setting work correctly. I also get warm air in the footwells, after several minutes. The only way for me to warm up the car is to run defrost to get the warm air circulating from the windshield, or to drive for a while until the warm footwell air circulates. Does this sound like a monovalve problem as well, or could it be some weird vacuum thing or a heater flap, as the center vents seem to be the problem?

BTW, the AC in this car works well, if it matters.

[wbain5280]

First you have to check for vacuum leaks. Then check vacuum motor/pod operation, solder joint problems in the CC buttons and finally replace any vacuum motors that are bad, which may just be the double acting one burried in the dash.

You might get user 'thomaspins' subscription because be has the complete procedures for this.

[gidpor]

to my understanding , the center vents will blow fresh air no matter what.
Sort of a protection thing. The only other air that comes out of there is the AC when on. Never hot air.
I also think (but not sure) that the mono valve is an all or nothing thing. It either works or not. Furthermore, if it is broken the system will go to default, which I believe is heat all the time. Therefore
I think your issue is elsewhere. Hope this helps narrow things down.

[fintail]

Thanks for the advice. I'll see what I can do.

Maybe that is true about the center vents. I simply closed them and the car gets warm inside much faster, and the windows don't fog as quickly either. I think I'll keep it that way for now. Maybe there's actually no real problem. It just seems colder in the car than in the past winters I've had it.

I have limited space, so I can't do a lot of work myself, and I'd like not to sink a couple grand into whatever this issue is. The car is quite nice otherwise, I can deal with this hopefully temporary glitch.

[jbaj007]

I'd check the two vacuum pods behind the glove box. It's not too difficult. Remove the glove box liner (5 or 6 little push pins) and unplug the glove box light. Almost sounds like one/both of these pods may be defaulting to "fresh air in".
A search will reveal a more comprehensive method of glove box removal, but you get the idea.

May not be this, but it's so easy to check.

I second wbain's recommendation for Pindelski.com for these types of 126 problems. It is very good. Best $30 you'll spend on repair/maintainance. FWIW

[fintail]

Thanks for the tip. I'll try that. Maybe this will be next year's project for the car.

I've also noticed the rear windshield is getting the tiniest bit of delamination discoloring, but I guess that's for another discussion.

[meltedpanda]

all of your vents should be placed in the closed posistion for the ACC to function properly.
The center vents should emit occasional warm air or AC blasts.
You also may have some diaphram tears on your vacuum units.
Your delamination is common, only repair to it R/R

[fintail]

OK I'll take a look at that.

Right now I am happy with simply closing the vents...they hadn't put out warm air in some time, and the upper vents are, so all is well.

This will be my next project, maybe I'll even take some pics to share as this seems to be a common issue.

I'm not going to touch the back window...when it comes to the point that most of the defroster elemts have perished, I'll simply take it to a shop and replace it, along with the seal, which I suspect leaks under a torrential rain anyway.