92 190E 2.6 - A/C blows cold through center vents, but hot through both side vents
 

HELP!!!

I have the same problem until now i don't have a clue on how to repair it.Sorry,Pls keep us posted if you find the solution.Thanks

Ron

It's a vacuum leak... do a search!!

A quick fix is to clamp the heater hose feeding your heater core (and unplug the power to the circulating pump) to overcome the malfunction of the heater monovalve, which has lost its vacuum source due to some sort of leak. Don't use this fix for long because the hose could get bruised, etc.

I can go into more detail on vacuum testing this system and a more satisfying temporary fix, as I just had this problem. Cheers, Andrew Seidel.

5banger:Could you tell me where is the heater hose is located and the circulating pump.Can you go into more detail.Thank you.

The quick-and-dirty way is to clamp the hose and disconnect the idle coolant-circulation pump as shown in the picture.
http://sio2usa.freeservers.com/mono.jpg

OR, the more detailed way is to start at the yellow vacuum check valve near the fuse box. There are two circuits to test. Disconnect both the green hose with red stripe and the red hose with gray stripe (on my '89 190e 2.6, anyway.) Use a hand-held vacuum pump to test each circuit's ability to hold vacuum. In my case, the red one that goes to a vacuum storage element was bad, so I just plugged that lead to the check valve so the rest of the system would work, as in the next picture.
http://sio2usa.freeservers.com/check.jpg
If it is the green line that won't hold vacuum, there is a lot to check out and you would want the manual on CD, or to take it to a mercedes tech. But first, sometimes, the gaskets in the monvalve itself go bad -- around a $30 part and a simple DIY project. Just follow the threads on the forum on how to get to the monovalve and check that it holds vacuum--if not, that might be where your leak is. Hope this additional information helps, as it may not be sufficiently similar to your model year. Proof that a hand-held vacuum tester is a must for the Mercedes DIYer! Cheers, Andrew Seidel.

Thanks...

That's the way they are
 

I believe the center vents on 190E/D do the heating and cooling work while the side vents are for fresh air...I may be wrong though...thats the way it was on my 1992 190E 2.6.

Jim
1992 500E

Jim: I think you also have a problem with your previous 190e.MY side vent blows hot air and the center vents blows cold air on A/C or heater.Thanks

Ron

Oh...sorry
 

I misread/misunderstood you...your side vents blow hot when AC is on? That is a problem. Mine didn't do that. Center vents blew fresh air which I'm told is normal. Definitely a vacuum leak. I fixed the problem by upgrading to the 500E!!!! Sorry I was no help. I'm an idiot. Hope you find the right fix. Tchuss

Jim
1992 500E:confused:

Both the 300D and the 190E that I had blow fresh air through the center. The side vents blow heated air. With the A/C on, all vents blow air through the cores. (I believe they are in the same air path)

I too, have a problem with my 190E now where it blows hot air through ALL the vents now. The A/C does cool it marginally. I have not had time to check the vacuum system for leaks yet as I am in the middle of taking the engine out. (Bent valves due to broken timing chain):mad: