Hi, guys this is my first post here. I've been lurking for months. Such a good forum you can pretty much get every answer to your questions by searching, but I was unable to find a answer to this one.
My car only blows heat. I just replaced the monovalve plunger, had it by-passed till the replacement arrived, and now it will not blow anything other then full heat.
Could this be a sign that my Climate control unit is bad.
Any input on how to proceed and what to check so I don't start throwing parts at it would help.
Again, great forum.
Samson

I'm going to go out on a limb and guess you own a Mercedes. Care to share which model it is with us? Maybe even the year?

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


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83 300D turbo. 123 chassis

'Any way you could have reversed the mono-valve connections?
(Praying for a quick,easy repair)

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'84 300SD sold
124.128

that would mean when I put it to full warm I should get cool air, and that's not happening. Heat, regardless of the temp wheel's setting.

I doesn't work like that, it's fully open with 0V and held closed with voltage. Have you tried measuring the voltage between the contacts at the monovalve in both the full heat and full AC positions?

I would check the connectors as they get brittle and the wires will pull out. As the previous post said, put the CCU on full cold then check the voltage across the wires. If you are not getting 12V then you either have a wiring issue or the CCU is no good. if you remove the CCU, the monovalve wires are on the right side connector if I remember correctly. I did a continuity test and found one had an open. Fixed it and the monovalve worked again.

There are detailed posts on how to resolder the CCU if it needs it.

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