Question about 2002 GMC Envoy
The running temp of the engine has little affect on the A/C. The condenser for the AC is in front of the engines' radiator, so in that respect there can be a negligible amount of heat transfer between the two. I only mention that as an FYI. Now, more to the point...the engine cooling system and the AC operate independently. The engine drives the AC compressor pump via a pulley. The pulley free-wheels until the AC is turned on and then an electromagnetic clutch engages the pump. That's why you feel (and hear) it engage when you switch on the AC. The pump actually draws a significant amount of horsepower from the engine...say maybe 10-20 horsepower. So your engine does work a little harder and will run a few degrees warmer (but not a lot). And that's why you don't get quite as good of mileage when using the AC. To me, it's worth it.
Now, if your AC is low on refrigerant (the 134A fluid that runs through the tubes under pressure-making it cool when it expands through an orifice as it enters a coil in the cabin area) it won't work so well. You also risk burning up your AC compressor if it's too low. If that happens, you'll know it because the pump will seize up and probably break the serpentine belt that drives it...causing a momentary sensation that the brakes are on. Remember it's driven by the engine via a belt. Once the belt breaks the alternator and water pump also quit because they depend on the same belt. You would certainly have warning lights on your instruments too. This is no time to drive it home or even another block for that matter. It's time to stop and turn it off, have it fixed without another minute of run time. If not? Well, read on.
If your engine is running hot, it's due to something else besides the AC. There are several possibilities but the AC isn't one of them. Overheating is the single most common cause of engine failure. Probably around 90% of engine failure is due to some form of overheating...compared to say, loss of oil. The bad part about overheating is that it sometimes sneaks up on you and it's often too late before you realize it. Believe your senses and the warning lights/gauges! If you shut off an engine before it sizzles, chances are you've saved it from serious damage. I'm talking about seconds, not minutes. And no, the light won't eventually go off if you ignore it, but you will be walking. If it's just running on the high side, have it checked out. A couple hundred bucks today may save you $2000+ next week. Again, it's worth it.
So, bottom line is this. If your AC is low on refrigerant it won't cool the inside of the car to well and that has little or nothing to do with your engine running hot. And NEVER ignore overheating!
Hope this helps. Jim-28 years A&P Aircraft Technician and lifelong performance automotive enthusiast. Good luck.
Posted on Oct 03, 2008
No not refregerant but yes to antifreeze
Posted on Sep 13, 2008
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