87 300SDL - I have heat up until 30 mph then it goes cold. I used to get up to 60 before this happened, but its slowly getting lower and lower. I changed the mono valve (it did have a tiny tear in the diaphragm) and thought that would take care of it, but no. Same thing.

The Climate Control Unit makes a lot of noise when its very cold outside. Clicking and clacking, fan turning on and off with clicking and more clacking. I'm thinking the CCU is bad (or getting there).

If I disconnect the CCU, should I then get heat full time? Then telling me the CCU is the problem?

Thanks for any help
Mike