This is just a thought, so I could be wrong, but I was wondering about the same a few days ago and started playing a bit with the knobs and settings.. it seems to me as if the automatic control overrules the hot/cold thumbwheel (as it didn't seem to make any difference) and that makes me think that the thumbwheel is only used if the automatic climate control is off, so you could get heat from the engine, or nothing at all, by adjusting that wheel. Again, it's a thought, not something I know for sure