whats the difference between "AC" and "MAX AC"

[mfp4073]

Um, yeah, what the title says....

[Pablo-UA]

on max ac uses air from cabine (there is air intake door under hood)

[Rockledge]

When MAX A/C is selected, there is no outside air allowed into the cabin, like Pablo said. The cold cabin air gets recirculated through the system.

In addition, the heater control valve (hot water valve) closes, cutting off hot coolant flow through the heater core.

[sorensenj]

Not trying to be a smarty here Rockledge but does that mean the heater coolant valve is open with the control on the regular AC? Seems it should be off whenever your in AC or Max AC. Thanks.

[sfcwoodret]

Max AC is good to use when your in city driving with all the pollution and smog.

[Rockledge]

Originally Posted by sorensenj

Not trying to be a smarty here Rockledge but does that mean the heater coolant valve is open with the control on the regular AC? Seems it should be off whenever your in AC or Max AC. Thanks.

Yea, it does seem a little odd that the hot water control valve only closes on MAX A/C, but that's how Ford designed it.

During normal A/C hot coolant still flows through the heater core, which means it's entirely up to the blend door to keep the warm air out of the airflow. That's why when a blend door door fails you only get hot air blowing out in all modes except for MAX A/C.

[jimdandy]

The cabin temperature is controlled by mixing hot air with cold, that is why the heater remains on. There is no control in the max position. If you are using the maximum position, the idea is to obtain maximum cooling, so the mixing would be unnecessary. Some other mfgr's use the mixture control in both postions. jd

[mfp4073]

I dont know if all cars are the same, but was driving last night and was wondering that! Was thinking it may have had something to do with the cycling of the compressor. Thanks guys!