looked in my owner's manual the other day. out of boredom, read the part about a/c operation.

more or less it said:
MAX - cools already chilled inside air. use when rapid cooling desired
NORM - cools warmer ouside air.

true, or just a dummy owner's manual explanation? i guess i'm asking what is "harder" on components. MAX AC, fan on 1 or NORM AC fan on 2 or 3. i always thought it was "easier" on the truck to have it on NORM, but the owner's manual makes it sound like the truck is working just as hard.

 

max is harder on truck.

 

How is max harder? Isn't it just switchin the air intake for the A/C system?

 

the system works harder, listen to it.

 

The compressor noise doesn't change, just the added noise of the electric fan blowin cab air into the A/C system.

 

agreed, but that puts more strain on elec. system which is working harder and that was the original question.

 

gotcha, so as expected the manual explanation is BS as i should use NORM when possible.

thanks guys

 

nah, you can use Max A/C, it's not puttin any more strain on your motor, its is just usin a little bit more electricty, but you altenator should be puttin out more than enough power.

 

ok, i went out and got my 94 f150 manual and my 94 explorer manual.

they both say that the 'sound' of the fan is more because it is not baffled and the explorer manual adds that the max setting 'has greater fuel efficiency'.

 

...i'm left confused. especially with the "greater fuel efficiency" line. if it's more of a strain wouldn't it be harder on the engine. (unless you just meant NORM)

 

The book is right.
NORM is harder on everything by a long shot (not even close).

When the A/C system is on NORM the compressor has to work a lot harder, You have higher head pressure and it cost you MPG is gas. You are always working your compressor to the max.

When it is on MAX once the inside gets pulled down there is less of a Temp drop across the evaporator and the head pressure goes down and you engine does not have to work as hard and the MPG goes up.

 

Max NOT more of a strain. Its about the equivalant of turning your stereo up louder with your headlights on. The only strain is on the battery and altenator.

Norm however is having to cool the air much more than Max, so the compressor has to work harder to cool the much hotter air.

 

There is less strain on the battery and alternator on MAX.
The fan does not have to work as hard to move the air and more gets moved.
It is wired the same to the fan motor but being a DC motor it speed is controlled by its load and voltage. With the voltage the same and the load on the fan less it is moving more air and using less current.

 

But don't both motors work when its on Max? The one to push cab air through the A/C, and another to push the air form A/C through the vents?

 

I think we are talking about an F series truck they only have one electric fan motor.
The only difference between NORM and MAX is that vacuum is applied to the recirculate vacuum motor in MAX and not in NORM.