AC Temp Settings
 

OK all -
I need someone to settle a feud between the Mrs. and I. I took my son's '99 Ranger in for an oil change yesterday, and when I got in I noticed he had his air conditioning on "MAX", but the temp was on full hot. I always thought that this was bad for the A/C, and mentioned it to him. My wife said she'd never heard of that and that the A/C could be used as a heater. Huh?? Please tell me she's wrong!

JA

prolly just had it set there to use the recirulation function...FWIW the only settings the compresser doesnt run is OFF and floor only...hes doing no harm to the a/c system

What the kid is doing is using gas to run the A/C, which will remove moisture and heat from the air (stops fogged windows) and then reheating the air to a temp that makes him happy. Or he doesn't realize he's got it on A/C when it's not needed, and is just wasting gas and $ for no good reason. Either way, no vehicle harm will be done. A/C is just a heat pump, removing thermal energy (ie, heat) from the air inside of the vehicle and transferring it to the outside. Now there were a reversing valve in the system, one that allowed the inside and outside coils to be swapped, and a few more details, you could fire it up on a cold morning ang get heat real quick like. Like the kind used in homes. But that doesn't exist today (that I've ever seen), and the A/C is not able to heat a vehicle interior.

*Maybe some high $ ride finally made use of this knowledge and has an awesome HVAC system.


Compressor doesn't run in the vent setting either.

Well there is a slight problem with all this logic. The heater core is bypassed when in the MAX A/C position. Vacuum is being applied to the heater control valve in this position, thus cutting off the heater core from the system.

So the only "heat" that you should have is the outside air temp.

MAX AC heater is bypassed you will get outside plus whatever the AC can do.
On AC you can use the heater, along wither every other setting for which the compressor is used. IE defrost and blending floor and dash.

So you are both right, I prefer to think you are both wrong though.

With it on Max A/C and all the way to the hot setting you will only get outside air temperatures is what I meant.

They use it on OTR truck reefer units. It would be nice to have in a car in Canada I would guess.

^^^A/C system reverses and discharges heat into a compartment rather than removes it?

Utilizing the AC with the heat on does not cause any problems. other than it blows hot dehumidified air out the vents. Ideal for those damp cold morning's when the inside of your windshield has some condensation on it or from heavy breathing with the windows up. You know, like when you've been parking with your date on those cold wintery nights. :27:

If I remember correctly air flow in max AC with the heat in high position would pull air from outside, through the evaporator (removing moisture from the air stream), then through the heater core. For removal of internal condensation it would probably work better with the AC in regular mode (recirculation) with heat on high if its cold. Otherwise, whatever temperature makes you feel comfortable.

You got those two backwards.....MAX AC is recirculation, regular A/C is outside air.

You know you've done a good job when its -30 C outside and all the "fog" has turned to a layer of ice on all the windows....

Just sayin:sly:

I wish my parents paid for my oil changes

I stand corrected...

Also, if I remember correctly, I believe in Max AC the hot water valve is shut off. so I guess you'll lose the heat regardless.