A bad short in the wiring
When alot of engine power is needed, the A/C compressor will be shut off to reduce engine load.
no but it can cause motor to lock up because no air flow
the AC is run by a belt that is connected to the engine. if you turn the engine off, the belt stops moving. No belt movement means no power for the AC. the fan will only blow air, not cold air.
why wont the ac compressor shut off stays on on all settings
There maybe air in the system, and its gathering in the compressor. That would be my guess, take it to a certified vehicle air condition specialist or your dealer.
Could be a defective voltage regulator (not opening when engine shutdown). I have seen many strange things caused by a defective voltage regulator (located internal to the alternator).
Yes, if the compressor's bearings are bad, usually accompanied by a roaring or squealing noise coming from the compressor's pulley.
DO NOT FEAR THIS !!! The ac comes on with the defrost: because do you ever use your ac in the winter? me neither. Manufactures have made the ac come on with the defrost to prevent the ac compressor from seizing up. Since we never use them in winter, at least in cold climates. Cheers and drive on.
Turn off the defroster.
Did you happen to move it to Defrost when you turned it off? The ac compressor also runs in the defrost cycle to keep the seals lubricated during the winter months when the ac is not used.
Is the AC turned on?