Fixed the "only have heat problem"
 

HI,
I just wanted to share my experience with you all and at the same time thank everyone for their input
THe vehicle is a 1983 TD wagon (123)
Poor heat control and discovered a ripped diaphram on the monovalve. Replaced and then I had great heat. Boy did I have HEAT!!!!
Could not regulate temp at all. The monovalve was never getting a Ground signal to close so It allowed full flow. I removed the pushbutton control unit and thanks to many members previous post I learned that when the unit is off, "O" pushed the monovalve should be energized. It wasn't.
I decided to go to my local friendly junkyard where I got my engine from and did some shopping. I pulled a pushbutton unit from a 85 CD and a Temp control box (silcver box behind glovebox) figuring it must be one or the other.
Well when I installed the pushbutton unit, that solved the problem. Everything works perfectly now. The temp wheel controls the inside temp perfectly.
I will add that before I installed the "new" CCU unit I took apart and cleaned the thumbwheel contacts. They were filthy. I have also replaced the foam tube that connects the dash temp sensor. Mine was as expected corroded and even broke in half.
I also notice now at nite that what ever button I have pushed in on the CCU, It lights up brighter to let you know what mode you are in. My old one never did.
I just wanted to share my results with everone and hopefully if someone else experiences the same thing, It will save them alot of diagnostic time.
THanks again to all contributors,
Mike Moran

Way to go! I have been avoiding my climate control issues for a while now. Mine is on "default" mode where I only get defrost, but the heat works great on that setting, so I have left it alone. I am going to look at a 1984 with a smashed drivers side that I can get for around 500 bucks. Hopefully, there will be some good parts on it.

I had the same deal with my 300-D. The only way I found to regulate the temperature during the winter was to roll down a window! That system didn't work that well.

I still remember driving back to the DC area from Philly in 20 degree weather. My clothes were soaked throughout from sweat!

i think if i ever found a junkyard with w123 mbs in it i would be in heaven:)

junkyards
 

It's funny, the yard I go to has at least 3 of them. I pulled the CCU from an 83? CD. Thats the 2 door model right?. What a shame, only had a minor hit to the door.
On Long Island there is alot of MB in the yards. I think alot were sold in this area.. Although I didn't see this particular car prior, the engine I got from them came out of an 85 with 112k on it. The guy who pulls the motors said it was a shame. The car was mint except it got hit hard in the rear. THey had it running in the yard and because it ran so well, they pulled the motor for resale. Lucky for me..... runs beutiful too...
Mike Moran