Should I turn the air conditioner off before shutting off the engine, or just leave it on all the time.
Not necessary at all .
I turn the AC off/keep the fan running a few blocks before home to get rid of the condensation on the system. Never like the mildew smell from leftover condensation with possible moldy stuff.
I don’t think it makes any difference. The compressor is going on and off all the time anyway by itself, plus the switch is the weak link.
This used to be relevant, or so I’m told, because back in the day- if the a/c switch was on, the a/c compressor was engaged during engine startup- causing lots of extra strain on the battery and starter.
nowadays, when ‘starting’ the vehicle, the accessories are off during the cranking of the engine at startup, and then come on when the vehicle starts.
That’s if the AC system is a Cycling Clutch Orifice Tube system.
Most vehicles today have expansion valve systems where the compressor runs all the time.
It doesn’t matter if the AC is left on or not.
The compressor gets no power when the ignition is in the start position.
Tester