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1990 190e
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Discussion Starter #1
I have a 1990 190e 2.6 with a couple issues I need some help on. I'm having a problem with hot air constantly coming from the side and defrost vents. I read one thread I found on this but the diagram is a bit different. I put vacuum on the main line and it held until the key was turned to the on position. I was able to test each line that I could see where they went to. What I am looking for is the correct diagram for the picture I have attached if anyone has it. Also, the piece that I have attached a picture of, can you give me the correct name for it and what are the testing procedures for it please.

Thank you for your help.
 

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1990 190e
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26 Posts
Discussion Starter #3
there ape mutli reasons for the hot air. I am having the same issue.
could be heater core
vacuum issues

Thanks, heater core just replaced. Now I am trying to test all vacuum lines and the box I have pictured where all the vac lines lead to. I need to know what it is, vac diagram and how to test it before I can go any further.
 

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190E, SLK350
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66,970 Posts
I think it is normal for hot air to come out from the defrost when you activate the button. This is the case with my 190E and 560SEL.
 

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1990 190e
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Discussion Starter #7
I think it is normal for hot air to come out from the defrost when you activate the button. This is the case with my 190E and 560SEL.
Just when you have defrost on. I have the A/C on and heat is constantly coming out of the side vents and defrost just as fast and hard as the a/c center vents. In other words, something is not working correctly. What I need to know is what is the part called that I have pictured and what are the testing procedures.

Thank you.
 

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96 C36, 87 Turbo'd 190E 2.3-16, 86 SC'd 190E 2.3-16, Brabus'd C32
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1,626 Posts
your a/c is dead. the center vents are just to let air in from outside (fresh air vents)
 

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1990 190e
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26 Posts
Discussion Starter #9
your a/c is dead. the center vents are just to let air in from outside (fresh air vents)
Meaning? My A/C works perfect. What is basically happening is there is either not enough vacuum going to the part that I have pictured or there is a valve that is leaking. I tested the one that cuts the defrost off and it also controls the side vents. Once I pulled a vacuum on the actuator that controls the defrost, it closed part that allows the heat to come through and allowed cold air through. I have a couple more test to run on it to pin point the problem.

Thanks
 

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'85 2.3-16 '99 C280 '11 GLK350
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Since the "doors" for the Tempmatic climate control system are opened and closed via vacuum driven diaphram switches (large pink/white drums) then you've either got a faulty switch or disconnected vacuum source.

The only way to service either is to remove the dash.
 

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96 C36, 87 Turbo'd 190E 2.3-16, 86 SC'd 190E 2.3-16, Brabus'd C32
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the center vents are not a/c or heat just outside air
 

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'85 2.3-16 '99 C280 '11 GLK350
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the center vents are not a/c or heat just outside air

There is A/C through the center vents . . . I believe you've confused it with "unheated air" . . . which means that heated air is only from the side vents, the floor vents and the defog on the dash.

The center vents provide outside air or chilled a/c.
 

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1990 190e
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Discussion Starter #13 (Edited)
There is A/C through the center vents . . . I believe you've confused it with "unheated air" . . . which means that heated air is only from the side vents, the floor vents and the defog on the dash.

The center vents provide outside air or chilled a/c.
Since the "doors" for the Tempmatic climate control system are opened and closed via vacuum driven diaphram switches (large pink/white drums) then you've either got a faulty switch or disconnected vacuum source.

The only way to service either is to remove the dash.
You're correct on the center vents. I have tested the 2 diaprams that I can see that are right behind the radio. They are holding a vacuum. Are there anymore diaphrams that I can't see? I am trying to find a diagram for this but can't seem to get my hands on one. I think I might have it pin pointed to the part I have pictured in my first post but not sure yet. There's a couple of vac tubes that I have no idea where they go to, so hopefully I can get a diagram. Luckily the A/C blows cold until I can figure this out, because it will not switch to heat. I have tried another A/C control and it did not change.

Thanks for the help guys.
 

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'85 2.3-16 '99 C280 '11 GLK350
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I seem to recall there being three actuators. One right behind the radio console; one up and to the right of the where the ignition key is and a third one up on top the heater box.
 

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1990 190e
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Discussion Starter #20
Ok, found two actuators that are not holding a vacuum. Would that cause the whole vacuum system to malfunction?
 
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