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  #1  
Old 12-20-2004, 01:07 PM
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Location: Charleston, SC
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No heat and I can't figure out why

I have read nearly 2 hours worth of posts on "no heat" and cannot find something resembling this problem.

Here is the symptoms:

1. good vacuum on the heater valve and on the vacuum line going from the valve. Hook it up and turn on the heat, the valve will not open.
2. Climate control head and aux water pump are new.

I currently have the Idle control valve unplugged to keep the car from stalling but don't think that is related at all.

All the fuses are good and I hear the flaps opening and closing when I change settings on the Climate control unit.

Why the hell don't I have any heat???????? It was 24 here in Charleston this morning and to draw a comparison, that would be like it being 50 below in Michigan. We just ain't used to this at all.

The only other thing I can think of is the vacuum distribution module.
Any thoughts would be appreciated.

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  #2  
Old 12-20-2004, 01:33 PM
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I don't know much about your 190E but I fix my 1991 560 SEL with a new mono valve repair kit from EBay ($18.50, delievered). It took me 20 minutes to complete the whole exchange.

In other words, check the mono valve out, it should not take you more than 30 minutes to be sure about the problem.
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  #3  
Old 12-20-2004, 01:46 PM
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Normally I would agree BUT the fact that I am getting good vacuum on the heater valve and the line tells me that the problem is not the monovalve having a rip in it. If that were the case I would not be able to get a vacuum the way I understand it. Also, is there a monovalve between the heater valve and the vacuum distribution module or does the vacuum line from the heater valve go directly to the vacuum distribution module?
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  #4  
Old 12-20-2004, 02:21 PM
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Quote:
Originally Posted by 190edude
Normally I would agree BUT the fact that I am getting good vacuum on the heater valve and the line tells me that the problem is not the monovalve having a rip in it. If that were the case I would not be able to get a vacuum the way I understand it. Also, is there a monovalve between the heater valve and the vacuum distribution module or does the vacuum line from the heater valve go directly to the vacuum distribution module?
Unplug the monovalve and see if you get "the green house effect"
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  #5  
Old 12-20-2004, 03:15 PM
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The heater valve should default to open. So if you have vacuum there when the heat is on then it is most likely the check valve for the heat system, the big one that is, or it is the CC Unit itself. Unplugging the vacuum line at the heater valve should open it up and allow it to flow. Of course then you will have a vacuum leak so plug the line after.
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  #6  
Old 12-20-2004, 04:09 PM
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Quote:
Originally Posted by TX76513
Unplug the monovalve and see if you get "the green house effect"

Help me out, which monovalve do I unplug?

Maybe if I put it this way it would be clearer;

Everything appears to be intact. With the heat set to max the heater valve is wide open, hot water is running through the heater core but the air coming out of the side vents is room temp at best. And I still would like to know if the vacuum line runs directly from the heater valve to the vacuum distribution model or just where it goes to from the heater valve. Vacuum diagram in the factory manual for the Tempmatic only shows the vacuum layout when the a/c is running.

Could this a blend air vent problem? If the monovalve that controls the blend air is not receiving any voltage won't it just stay where it was the last time it had voltage to it?
Just another train of thought if anyone has any comments on that angle.
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Last edited by 190edude; 12-20-2004 at 04:20 PM.
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  #7  
Old 12-20-2004, 04:28 PM
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Looked at a diagram of 190 looks like you have two vacume Heater Valves and not an electrical monovalve (like mine). If you have tested the heater valves with a miti vac and all is well. Do a search on the CCU REPAIR there is some valuable infor there.
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  #8  
Old 12-21-2004, 09:29 AM
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Did you check the fuse on the CC Unit? Also this whole system is vacuum, no electronics other than the CC unit and the Check Valve control the system. The CC unit tells the Check Valve which lines to give vacuum too and how much so that it will open the vents as well as control the blend air flap! The blend air flap has a potentiometer on it that will tell the CC what position it is in so the CC can move it to keep the temperature in the car at the desired setting. There are two temp sensors, one in car and one on the top of the fan housing for outside air temp. The CC controls the blend air flap based on input from these two sensors and the potentiometer on the air flap. To get to that potentiometer and flap you can either remove the whole dash or take the glove box out and it is on the left top right below the dash top. It is easier to see and test with the dash removed, plus you can check all vacuum lines and connections this way. There is a full vacuum diagram on the MB Maint CD for the W201 model. Even has what color the lines are. I suggest you pick up the maint CD if you do not already have one, it is very helpfull when troubleshooting this stuff yourself.
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  #9  
Old 12-21-2004, 10:34 AM
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The CCU in my car does not have a fuse. I just replaced it this past summer and the aux water pump so I know those are good. Some of the long time MB wrenches on the MB mailing list seem to think it is likely a blend flap problem. Will have to check the monovalve that controls that when I get the time to take the dash out. Unless somebody knows a way to check that one with out doing that?????
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Smoked corners
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  #10  
Old 12-27-2004, 06:51 PM
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Location: Ladera Ranch, CA, US
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Why not change the ($10) cabin temperature sensor?

Silly thought here. After changing out the monovalve (both the kit and the whole shebang) on my '86 W126, I still had heat problems, as well as the blower motor blowing at random. I changed the $10 temperature sensor, which is located in the dome light assembly. Remove the assembly as if you were changing the bulb and you'll see a plastic elbow at the end of a thick rubber tube. Detach it from the assembly and tube, put the new one in place, and you're done. Just be careful of the brittle plastic!

I also did this to my uncle-in-law's '87 420SEL. Since this simple repair, our climate controls have worked liked champs!

- Casey

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