Sorry Steve, but the max air setting does NOT pull less power from the belt as it is only a blend door function. It will not have any affect on the engine, compressor, blower or belts. Fan speed will remain the same, no matter if on max or normal cool. Blower will work the same in any fan speed setting as far as pulling air across evaporator core. All max air does is shut the outside air from blowing across the evap. coils and of coarse recerculating the cab air. Now, that will cause the compressor to cycle off more, so if that's what you are saying, my apologies to you. Btw keeping it in max air will sometimes cause the coils to freeze up from all the cold air,and then it will feel like it's not working

 

All max air does is shut off outside air and recirculates cab air. When compressor clutch is engaged and max air is set, it will drag on engine same as normal cool setting will. Max air will NOT have any affect on the compressor other than making it cycle a little more. It won't have any affect on fan speed either. Like Shane said, clutch is either engaged or disengaged. You won't be using any more gas in max air than you would on a normal air setting, high or low fan speed. And the outside temp is a factor as well, if it's say 100-105 degrees outside, comp. clutch may never cycle

 

at least on my 03 Ex. Setting the selector to Max air actuates a vacuum switch on the heater hose line. It shuts off the flow of hot water to the plenum thus allowing ONLY cool air from the evaporator, which is then recirculated in the cabin since it shuts off the outside air inlet.

It is my thinking that the compressor cycles based on the drop in pressure, which is based on the rate of heat exchange in the refridgerant. If the refridgerant (geez I can't spel) isn't warming up as fast, then the compressor won't cycle on as often, and therefore, there will be less drag on the engine during a given period of time, compared to a blended, outside air being constantly cooled anew. In that regard, I think it will save some gas. Question is, how much???

Maybe it just feels like we're saving, and that's ok

 

Not sure about the expy's, but heater core air is not mixed w/ a/c air unless on the defrost or warm setting or there's a door stuck open. The refridgerent is not affected by the heater core and so no pressure on the a/c lines is affected. The pressure on the lines is dependent upon air flow through the condenser coils, rpm's(or how fast your compressor is pumping refridgerent), the trucks cooling system( condenser sits in front of the radiator) and outside air temp. Question: is there a bypass valve on your heater hoses, because your cooling system is based on continuous flow and shutting off flow to the heater core would put a block in that unless you have a by pass somewhere in the lines. I'm really curious about that as I have never heard of a system like this before. Thanks in advance!