A/c

why is it unwise to use the a/c with either the windows or the top (convert) down? (this is for my girlfriend’s edification)

Thanks

The AC system doesn’t care if the windows/top are down when being operated. Just as the heater system doesn’t care if the windows/top are down when being operated.

Tester

Running the AC will just use more gas, otherwise not a big problem. AC compressor may run continuously if the car never cools to where you have the temp set, therefore this could wear out the compressor and other parts earlier than they’d otherwise wear out.

On the Ford Mustang, just like most cars, the AC compressor does not turn off when you reach temperature. Why do people keep thinking that car AC works like their home AC?
The AC compressor will cycle off briefly if the evaporator reaching freezing temperature, but that’s not going to be affected by temperature setting or having the windows open or closed.

Another thing to consider is that the A/C is dumping heat ahead of the engine radiator so the engine will run hotter and overheat and boil over if the cooling system is marginal.

Ever wonder why the State highway department puts up signs before long upgrades to “Turn off Air Conditioning”. Not only will the engine have more power but a poorly maintained car will not boil over and stall.