I remember once reading that the "max" air con setting recirculates interior air and the "normal" setting draws in outside air. But now I just read the opposite. Anybody know which is which? Anyway the book I just read also says to use the outside air initially to more quickly cool down the interior, then switch to the other.

 

My books tell me that "max" recirculates inside air and is the fastest way of cooling the interior. Open windows for the first few minutes of driving to speed removal of stale hot air. Normal uses outside air to cool the vehicle and is quieter than "max" but not as economical.

 

Thanks. I looked in the owners manual and it is exactly as you say.

 

Ok, so MAX means recirculate inside air and A/C means pull in outside air. We understand that MAX will cool the vehicle quicker but prolonged use can bring moisture concerns.

What else is different between the two? I thought MAX also means the compressor is running 100% and A/C means it cycles off and on, much like the a/c at home. Why does the owner's manual say that MAX is more economical?

 

On max a/c, the moisture level in the vehicle should get very low. As the same air recirculates over the evap coil, it will lose more of its moisture in the form of condensation, which in turns drains out on to the ground. The only concern I can think of would be leaving the vehicle sitting unused for a while with the selector in max. If condensate was left in the airbox, it would stagnate and become rather malodorous.

The compressor will run more on norm than on max. It goes through the same process of cycling when needed, but when you are cooling air that is already cool, there is less heat to remove from it. This makes max a/c more efficient than norm. I know that is pretty basic, but it should give you an understanding of things.

Personally, I run norm when I smoke in my truck to force the smoke out of the cab, but max at almost all other times.

 

I think the MAX setting also shuts off coolant to the heater core, by way of a vaccuum valve (which is why you should never run plain water as a coolant if you have AC).

Steve

 

The Ford manual says that Max cools more quickly than Normal, but that for regular operation, Normal is recommended. So there must be some reason not to use Max all the time. Does anyone know what that reason is?
Frank.