I know driving with AC reduces your gas millage... does it make a difference with how high the AC is set ???

 

The A/c clutch has two settings, on and off. You may see a small reduction in mpg through alternator drag spinning your fans harder with a higher setting... but in practice. Not really.

 

If you drive with the windows down and AC off the gas mileage is usually worse then using the AC.



Setting the AC to colder only runs the compressor harder if the fan speed is up. Low fan speed=minimum AC clutch on time.

 

Mythbusters tested the whole windows up/down, A/C on/off thing. Check their website for details.

 

If he has climate control yes (I am pretty sure my honda turns its compressor on and off), his tiburon / my 03' XD and 09' HD with fan speed controls... no. The clutch stays on until you turn it off.

 

What happens when the pressure gets too high?

 

It has pressure safety switches, but have you ever watched the pressure gauges on an A/C? What causes more pressure.. fan on low or revving the crap out of the engine with the a/c on? I know on mine the A/C does not shut off at higher RPM. The only car that I have owned that did that was my mazda. So low fan speed would cause a higher pressure increase than reving it and spinning the compressor faster?





Maybe I have never had that happen because where I live the ambient outside temps are more than enough to keep it from freezing up the condenser.. ever?