1985 190d COLD AIR ON FEET - PeachParts Mercedes-Benz Forum

vtmbz · #1 11-13-2010, 02:36 PM

Now that winter is nearly here-- I seem to have no hot air on the floor, only cold, and cold air oozing out of the ashtray area. PO put in a new climate control panel at some point. Otherwise the ccu seems to be working well.

Where do I start searching for this? With the ccu off, no air movement. Only when I select for floor heat do I get this condition. Thanks!

Jeremy5848 · #2 11-13-2010, 03:05 PM

I had a similar problem with my '85 300D-T (W123, OM617). The vacuum pod for the floor vents failed, leaving the system normal except for no floor heat. In snow country that can be brutal. I was able to disconnect the throw rod and jam the doors open until I could get a new diaphragm for the pod. Depending on the pods used in your car, you may be able to replace the diapgragm or you may have to replace the entire pod.

It is also possible that it is an electronic problem in your PBU but I'd check the vacuum pod first. A Mity-Vac is a useful tool for that; if you can't pull a vacuum on the floor pod then the diaphragm has failed.

Jeremy

vtmbz · #3 11-14-2010, 09:06 AM

Thanks for that I will investigate. I wasnt sure where to start and didnt want to rip out the dash for nothing. I have a parts car with the ccu out so I can try a dry run if needs be. I once had a car that was so cold I had to drive it with a sleeping bag over my feet. ( I cant believe I DID that)

Jeremy5848 · #4 11-14-2010, 11:21 AM

We drove from northern California to Utah wearing 'moon boots.' The upper part of the car was fine but the floor was freezing. Once we landed in Salt lake, I was able to wedge the floor doors open and we had floor heat for the return trip.

Put the passenger seat all the way back and lie in the footwell. You will be able to see the footwell outlet and the rod that opens the door (the vacuum pod is on the driver's side in the 123 but may be behind the console in the 201, I've never seen one). Popping the rod out of its socket will allow you to wedge the door open. Do the same thing on the left side.

When you have more time, replace the pod. You should be able to get a new one from the "buy parts" link at the top of this page and that also supports the forum.

I think the 1985 201's climate control is in some ways a predecessor of the 124. Early 124s have two vacuum pods for the floor vents. They are just under the PBU. Removal of the ash tray, radio, etc., will be necessary to get at them.

Jeremy

vtmbz · #5 11-21-2010, 03:53 PM

Spent the afternoon dismantling the upper console to investigate. I used a heat gun to soften all the plastic and rubber parts; this helps keep breakage to a minimum especially in below freezing weather.

Pod held vacuum. Removed glove box to chase vacuum line to underside of dash. Dont think I have vacuum anywhere. Ran out of time and tied off the footwell flap with a tiestrap, which opens both sides. This works fine.

But, with no vacuum anywhere, I wonder where the next junction is? Not under the passenger side floor mat. Schematic indicates that the vacuum reservoir (I assume thats the same one that controls the locks) also supplies the hvac system, but where they meet I cant say. Am I right in thinking the electric vacuum pump for the central locking also supplies the hvac?

The good news is that I have an unmolested vehicle, so wires go where they say they do in the manual!