No benefit at all. When not in use, the compressor pulley is just an idler pulley and causes no drag on the engine. The AC is supposed to run in defrost mode to remove humidity from the air before it gets blown onto the cold windshield where it will condense and cause fogging.
February, 3, 2011 AT 9:09 PM
Thanks. Re defrost mode this is a wrangler with no doors and a bikini top, so that has not been an issue her in S. FL/
February, 3, 2011 AT 11:24 PM
Please can I come down by you! I'm stuck up here in WI where they throw a ton of salt onto an ounce of snow.
I bought a new 1980 Volare and didn't have much trouble in winter unless it was on a long drive but in the summer it was common to have to carry a rag to wipe the inside of the windshield. That car doesn't have AC. Later I started driving my ma's '78 LeBaron with AC and was surprised to see windshield fogging disappear within about five seconds after turning on the defroster. That one does have AC.
What I forgot to mention earlier was the confusion about air conditioning and fuel mileage. When you're not running the AC, there is no added load on the engine. Some people use an idler pulley and a shorter belt thinking bypassing the compressor will save fuel, but the fuel mileage loss is related to the other stuff on the vehicle. The radiator will be bigger and heavier, and the suspension system will be beefed up to handle the extra weight. THAT'S where the drop in fuel mileage comes from when you're not using the system. That's also why years ago you could buy add-on AC systems for half the cost compared to ordering it already factory-installed on the car. From the factory, the car comes with a larger alternator, stronger front springs, a larger heater box with associated extra controls, bigger radiator, possibly a second cooling fan, and tinted windows. That's why it used to cost so much to add AC to a new car when ordering it out.