Quote Originally Posted by Top_Fuel View Post
I've often wondered how the system actually works. My philosophy is that I want the HVAC doors to operate as minimally as possible...because the more they move, the more they are likely to fail over time.

So I never use the AUTO setting, I always have the air coming out of the dash vents, and the temp is always set to 89 in the winter. I assumed this would always keep the blend/mode doors in the same position...with maximum airflow over the heater core. I have no idea if this is actually how it works or not. The service manual can be frustrating when you want a text explanation of how something like this works.
I keep mine set at 80 with the flow set to defrost/feet with the fan set on 3 bars. Doesn't run the AC compressor. I'll turn on the AC momentarily to provide extra defrosting the windshield but most of the time it's not necessary. I never use the auto feature also.