Because it might overheat or need a break.
A lot of vehicles will activate the A/C compressor in 'Defrost' mode. Either Bi-Level or defroster will turn on the A/C compressor. I know in a lot of GM vehicles, even just the floor selection will turn it on.
Do you mean that the AC clutch does not engage the compressor? Or do you mean that the AC compressor won't turn even if the clutch is engaged? If the compressor is siezed and will not turn even if the clutch is engaged, the only choice is to replace the compressor. If you can turn the compressor by hand (understand that the belt pulley will turn freely with the engine if the clutch isn't engaged) but the compressor clutch isn't engaging, it might just be out of refrigerant. There is a sensor, usually somewhere near the receiver/dryer) that detects the "low side" refrigerant pressure. Once the refrigerant pressure at the sensor drops below a specified level, the compressor will not turn on. In other words, if the compressor clutch won't engage it might just be out of refrigerant.
Yes just as long as you do not turn on the a/c..............
bad motor or capacitor
Open drive.
open drive
A stuck compressor contactor. Do not turn off the indoor fan until you have either shut off the breaker or pulled the fuses to the outdoor unit and stopped the compressor, or damage may result.
That depends on what you're trying to do. If you just want to make certain it doesn't turn on, unplug the clutch wire at the front of the compressor.
If the A/C system is empty the compressor will not turn until you get enough refrigerant in it. Just turn on the A/C and hook up your can of freon. Once the freon starts filling the system the A/C clutch will engage.
When you turn on the AC, check to see if the compressor is running. If the compressor clutch is not engaging, it might be as simple as low refrigerant level. Automobile AC is not like a home AC. Since the compressor cannot be sealed, the seal always leaks a little and you need to occasionally add a little refrigerant.
Turn it off.
If the compressor is going out it can cause the belt to squeel as it's harder to turn the pulley when enged, or you could just need a new belt