This is an intermittent problem which started a month ago and keeps getting worse. Everything works fine with the Climate Control when the car is started. The heat is good and regulates itself for about 45 minutes. After that it blows cold air. I have tried pushing different buttons, turning the ACC off then on, shutting the car off for a few minutes to no avail. The only thing that works is to shut the car off overnight. Then every thing will work fine for 45 minutes to 1 hour till the problem starts again. Some help, it's cold outside.

Sounds like it may be the CCU. Mine have done that in the past in some W126's. I've had some success removing them, and re-soldering connections inside. Sounds like its getting warm, and having connection issues.

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D

The CCU is the push button unit, correct? Seems when I had the car apart there is a computer module behind the glove compartment. What does that do and could it be the problem?