Climate control fails to full heat?

My '97 e36 318is heater won't produce anything but full heat. I have changed both the control panel and the heater valve with no luck. Initially, after changing the stuff, the heater stayed cool until I turned it up and there it stayed until one sub-zero day in December when it wouldn't warm at all. I fiddled with the controls and it came back and has stayed piping hot ever since. The car doesn't have climate control, just the basic poverty-spec heater. Any advice would be gratefully appreciated. thanks.

__________________
This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW Heater Valve Cleaning/Flushing

[Wayne 962]

I'm not sure about this one. On some of the German Porsches, when there is a fault in the climate control unit, the whole system fails to full heat. The theory behind this is that in the German winters, it is far better to have full heat and not freeze to death, than have no heat at all. That said, I would guess that maybe one or more of the sensors feeding information to the system are faulty. You'll have to go through each one and test them, just like I've done in the past with at least one of my Porsches.

- Wayne