AC causing RPM drop and engine temp

[Chad Gervais]

Hey,

2004 GT2 owner here, 211,000 miles original everything.

Ive noticed since the weather has warmed up and im using the AC that when im sitting in traffic with the AC on, my rpms will drop for a second from about 800 to just over 500. It does this every few seconds while im at idle and never at speed. My batter volts also drop from 14.10 to 13.70. This does not happen if the AC is off.

Is something on its way out?

I also noticed yesterday while sitting in Boston traffic that with the AC off my engine temp will spike up to 220 and drop back to 210, when the AC is on it hovers between 195 and 200. I thought AC put more strain on the engine causing it to run hotter in hot weather? On the highway it makes no difference, it goes to 190 and stays put. I got to sit for about an hour in traffic that was moving at most 10mph so i had time to observe this stuff.

 

[indygrandprix]

When your not running a/c the radiator fan kicks on at 220 or so degrees when you run the a/c the fan turns on because it has to pull air over the condensor in front of the radiator to cool the refrigerant which also cools the radiator at the same time. When your on the highway it stays around 190 because there is always airflow over the radiator. The temp may be slightly higher when you have the a/c on during highway driving than with it off because the condensor heats up the air before it flows over the radiator.

I'm not sure on the voltage part. someone else will prbly have input on that

 

[TEK310]

he is right about the fans cooling your car

how long has it been since you replaced your thermostat? also the idle drop with load, sounds like a clogged IAC valve. (idle air control) take off your intake tube at your tb. is it real dirty? if so, take your throttlebody off, take off all your sensors (tps, iac, maf, etc) and soak it in carb cleaner. clean the iac valve too, the cone shaped end that goes into the tb.