Yet another A/C Climate Control Problem for 190/201 - PeachParts Mercedes-Benz Forum

orangedawg · #1 12-16-2003, 02:37 PM

I have a 1986 190e that I've been working on. I've read almost all the posts and info regarding the numerous A/C issues with these cars. My situation:

1. Car only blows hot air. It will at times get cooler (slightly) but maybe that's due to the engine thermostat opening/closing?
2. A/C compressor only engages when the top of the three right side buttons is pushed (the defrost button?). Pushing the middle snowflake button does not kick in compressor.
3. I can hear the vacuum "thing" behind the glovebox actuate when the control panel buttons are pushed, but I'm not sure what it's doing. It does not seem to change the location of the air in the vent, although it does come out of the floor vents sometimes, but it's ALWAYS coming out of the windshiled vents, no matter what button is pressed (except of the off button).
4. Main issue is that it is ALWAYS blowing heat.

What I've done:

1. Replaced the heater valve under the hood. Didn't change a thing, although I would note that vacuum is never going to that valve to close it allowing cold air to get in (is that right?) no matter what the dash setting is.
2. Replaced the climate control panel with a used one that I was assured worked. No chage in problem.
3. Inspected fuses and none of the them appear to be broken and contacts look okay.

Next step? I'm really getting frustrated and don't know what the issue is or what to do. I know this has probably been covered before on this list, but I nee somoe help, please? TIA

mbdoc · #2 12-16-2003, 05:57 PM

The W201 A/C/C system is unique from other MB's in the fact that to turn the heat off, vacuum must be applied to the blend air door vacuum element. By doing that the "FEEDBACK" potientiometer signals the pushbutton control & then IT shuts off the heater valve with vacuum. LOSS of vacuum to the blend air door element is the most common problem.

orangedawg · #3 12-16-2003, 07:17 PM

How do I diagnose/fix the vacuum problem? Is there someplace I should look first? Any help is GREATLY appreciated!!

euronatura · #4 12-16-2003, 08:10 PM

Orangedawg

MB Doc knows is stuff as many others do on this website. All I can offer you is my experience with my A/C System on an 88 190e - W201.

If you really do not know what you are doing I recomend that you spend the $ to get a proper diagnosis. From there if you want to do the work yourself, that it upto you since repairs for this sytem can be costly due to labor, not so much in parts.

I took my car to get diagnosed and what the tech did was verify vacuum through the (do not remember what it is called) but it is a central vacuum thing-a-ma-gig that is located behind the glove box. (access through the glove box) From there the tech told me which modulators/actuators would not holding a vacuum. There are three modulators/actuators located behind the dash. I do not remeber exactly but either one or two of these where the problem. Also the heater actuator/valve you call it was out. The Heater valve was the most expensive. The three behind the dash ran me about 20-30 a piece. I ordered all three that are located behind the dash since to change just one of them requires removing the dash so while we was in there, decided best to change all three and not ahve to take the dash apart again.

So in end, what I recomend is that you have the vacuum system checked through the main vacuum thning-a-ma-gig behind the glove box. Also that main vacuum thing-a-ma-gig needs to be checked because if it is bad then the other actuators do not function properly.

Also, you should have checked is the Klima Control Relay located (in my car) behind the batery close to the OVP relay. Now that I remember this was not functioning properly also. I changed it though I have read here on other threads that people have resoldered with good results. Also, the climate control push button can be resoldered with good results - at least from what I have read on other threads here.

Once again, if you really do not know what you are doing have it checked otherwise you can just be throwing $$$$ til you get it fixed and the labor on this repair is alot and some of the parts can be pricy too.

Iggy