Thanks, I will check my mono valve. In the mean time I took apart the Climate Control from the 87' 300D and found a "fried" section near a few solder points. It is safe to conclude that was my problem with regulating the temp.

Since my '90 300D 2.5 woked in the '87 is this interchangable totaly....will this affect any sensors??? Does anyone have access to an Electric Diiagram for these unit, or even where they can be purchased.

I could not find a model # on the '87 climate control, but after doing some research, I found that the ones they sell for the '87 300D is # 124 830 18 85. Can I insert and use the:
# 124 830 08 85, which is for: 1986 300E & 1987 260E & 300E.
OR can I use the:
# 124 830 33 85 which is for: 1988 - 1995 260E, 300E, 300CE, 300TE 300E 2.8, 300E 3.2, E320.

Fianally my current Climate Control is in Celcius, will I be able to use one that is in Farenheight?....Is it just the sticker? The one from my '90 is in farneheight and worked fine. I don't wana find out that in the summer the A/C aspect of it is messed.

I am not sure what my outside temperature display is in the instrument cluster, whether Celcius OR Farenheight since it is burned out. I am interested in purchasing a used working one and would like to know if mine is indeed Cecius then will one that diplayed Farenheight in the previous car work in my '87???

Thanks to EVERYONE!!!