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  #1  
Old 06-03-2001, 03:02 PM
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Join Date: Jun 2001
Location: kansas city mo
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Please Help

On my car the a/c blows cold out of the center vents and mild temp out of the side vents. I checked the vaccume going to the heater valve in the cowl area, and it isnt getting any vaccume. I traced the vaccume line to cab and underneath the dash on the passenger side into a box, it had another vaccume line going to it, i tested it and it has vaccume. To get by for the time being, I ran a vaccume line from the main vaccume source to my heater valve and it is closing completely but the side vents still do not blow cold. I would like to fix, I dont know what is wrong, can anyone help?
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  #2  
Old 06-03-2001, 10:20 PM
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The problem you describe is not uncommon with 190s. The TCC system in that car does require special test equipment to diagnose. Commonly this problem is caused by 1)a vacuum leak 2)a faulty potentiometer on top of the case which in a round about way causes no vacuum to reach the heater valve to close it. Also heater valves do go bad internally, which allows hot water to flow thru the heater core, AKA HEAT out side vents. Fortunately the heater valve on that car is inexpensive. If you physically pull up on the lever on the side of the heater valve and hold it closed for several minutes, the heat should diminish to none out side vents. The problem with your by-pass fix is, if you do not have a restrictor or a check valve in the vacuum line to the heater valve, when you accelerate you will dump the vacuum that is keeping the valve closed and you heat will momentarily come back.
It might be costly to diagnose and repair this problem, then again maybe not. Let your trusted MB tech find the problem for you, then make the decision yeah or neah.
Hope this helps,
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  #3  
Old 06-04-2001, 04:42 PM
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Location: kansas city mo
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I just cannot figure out why i am not getting any vaccume to the heater valve, like i said, where the line that runs the heater valve comes out of is a little box underneath the glove be that that box, could it box is bad? because it has 2 lines going into it, one must be a constant because it has vacume, it just isn't getting through to the heater valve line. But I suppose that little box probably gets controlled by the main controll cluster so i guess it could be that too.... hell i dont know, all i know is it is about 400 miles to the nearest mb dealership so i need to fix it if i can, is there any way i can test this stuff with a multi-meter and a schematic? Thanks for your time
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  #4  
Old 06-04-2001, 04:45 PM
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Join Date: Jun 2001
Location: kansas city mo
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I also thought that since this is a diesel and the vacume comes from a vacume pump that it wouldn't loose vacume at full throttle, so thats why i didn't use a check valve.

I dont know if it is supposed to, but with the ac controlls on, the heater circulation pump (on passanger side) is running.

[Edited by diesel lover on 06-04-2001 at 09:04 PM]
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  #5  
Old 06-06-2001, 10:59 PM
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Glad you called me out on that diesel vacuum pump mistake, I forgot it was a diesel, OOPS!

I don't have a TCC book in front of me at the moment, so I'll have to look at one tomorrow to be more specific.

Start simple, Check fuses - even if it looks OK, replace it fuses are cheap!

You could still have a vacuum leak in the system, or an electrical problem in the pushbutton assembly. You can order a manual for the TCC system from your MB dealer or Baum Tools 1-800-848-6657. The manual will have electrical diagrams and vacuum diagrams as well as function tests and theory of operation.

Based on what you said regarding the heater valve, it sounds like it leaks internaly, so replace it.

I will look into it some more tomorrow and let you know if I think of anything else that might help.


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  #6  
Old 06-07-2001, 11:50 AM
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Location: kansas city mo
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Thank you, I will get some more fuses and replace them so I can rule that out. I ordered a new valve so that should fix that problem. How much would this TCC thing cost?
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  #7  
Old 06-08-2001, 12:42 AM
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You are welcome.

You can order the manual from Mercedes directly also, find them on the web. The cost should not be too much. The problem with you attempting to correct this problem is the test cables and breakout boxes needed are expensive and only work for this application, so not practical. I still think a visit to a compitent tech. would save you money and time.

Sorry I couldn't be more help,
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  #8  
Old 06-08-2001, 11:35 AM
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Location: kansas city mo
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Well, I guess every-thing is ok,last night I was driving around and everything started working perfectly, vents and so on, so I the vacume ostopped and checked n the hose that is supposed to run to the heater valve and it is also working, I must have had a bad connection, or something like that. I guess I will just let it be and pray it dosent mess-up again.
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  #9  
Old 06-11-2001, 11:28 PM
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Location: kansas city mo
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Ok hold on, I have driven my car alot lately and my problem is a little more narrowed down. When it isn't going great, the controlls on the dash that change where the air goes to (defrost, floor, dash) quit working. On the a/c position, air comes out of the dash and defroster vents, and it won't direct air to different vents on other settings. Another thing it does when it isnt working is it shuts off vacume to the heater valve, and the temp selector doesn't work. The blower motor works no matter what so I guess it couldn't be a fuse. But then most of the time it works just fine and their isn't any problems. Any help?
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  #10  
Old 06-13-2001, 08:59 PM
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I would say based on your latest info. that you are experiencing an intermittent loss of vacuum. This could be from a leak in the system (0r any other vacuum system that the pump is used to operate)or from the vacuum pump intermittently not operating (bad check valve on pump). The TCC system has many vacuum lines and a storage tank ( I think behind the left front fender, look for a red vacuum line coming from the vacuum fitting at the firewall going to left front fender near hinge). If you purchase a vacuum gauge/hand pump it will help you with finding this problem. You could then disconnect the lines one at a time and test them to see if one is leaking as well as see how much vacuum the pump is generating. When the TCC system quits operating, does the brake pedal get hard to push? (Like it has lost it's power assist). From the vacuum distribution block behind the glove box you can test the individual flap actuators, but you will need a vacuum schematic to see which cells you are testing so you need a manual.

Keep checking you will find it,
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  #11  
Old 06-18-2001, 11:32 PM
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Join Date: Jun 2001
Location: kansas city mo
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Thanks for the help, the brakes have never got stiff on me so I dont think it is the pump..
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