Registered User
Not particularly. If you are at WOT the compressor turns off too. On a hot day, gun your car for a good few seconds and you'll feel the warm sticky air start pouring in 
G Kreuzer
Fiction!
No extra wear is done to the A/C unit due to the ignition ON/OFF cycle other than the normal wear and tear of running the A/C in general. SaltiDawg is also correct in pointing out all non-critical electrical units are effectively cut-off during ignition-ON. In addition, the A/C compressor also has a magnetic clutch that engages/disengages as needed. Upon ignition ON, the clutch is disengaged (compressor is not turning). The same clutch mechanism is also used for climate control purpose in the 'Econ' mode as well as reducing parasitic loss when engine power is demanded (i.e. WOT).
As a side note, while the disengagement of the A/C clutch restores the power loss during WOT condition, the ECU could cut back some ignition timing (if outside temp is also above a set value) ... anticipating detonation from the 'summer condition'. So, it's still better to cut A/C to insure maximum engine power at a given time.
No extra wear is done to the A/C unit due to the ignition ON/OFF cycle other than the normal wear and tear of running the A/C in general. SaltiDawg is also correct in pointing out all non-critical electrical units are effectively cut-off during ignition-ON. In addition, the A/C compressor also has a magnetic clutch that engages/disengages as needed. Upon ignition ON, the clutch is disengaged (compressor is not turning). The same clutch mechanism is also used for climate control purpose in the 'Econ' mode as well as reducing parasitic loss when engine power is demanded (i.e. WOT).
As a side note, while the disengagement of the A/C clutch restores the power loss during WOT condition, the ECU could cut back some ignition timing (if outside temp is also above a set value) ... anticipating detonation from the 'summer condition'. So, it's still better to cut A/C to insure maximum engine power at a given time.
Registered User
Quote:
When the Ignition Switch, a four-position switch, is turned to the "Start" position all electrical loads that are ignition switch dependent are disconnected except the starter solenoid.
In other words, while the starter is engaged, loads such as the stereo, wipers, A/C clutch solenoid, etc are disconnected! Loads that are not ignition switch dependent are either on or off as determined by the operator - headlights, interior lights, horn, etc.
that may be the case for the exact moment when you start the car. however, for the second(s) prior to the starter engaging while turning the key, some "juice" is being used up by whatever is on (e.g. stereo, wipers, or a/c). hasn't anyone been in a car that hasn't been driven for a few days and tried starting it with the wipers, stereo, and heater left on by the wife? you can actually feel the car struggling to start the car...there's enough juice in the battery to start the car but it just feels like barely. however, when i've entered my wife's car and made sure everything is off before starting the car, it starts without struggling. i'm just talking about those rare and few instances where the battery may be low on power. with everything on, you may not have enough "juice" to start the car. Originally Posted by SaltiDawg
This is not correct.When the Ignition Switch, a four-position switch, is turned to the "Start" position all electrical loads that are ignition switch dependent are disconnected except the starter solenoid.
In other words, while the starter is engaged, loads such as the stereo, wipers, A/C clutch solenoid, etc are disconnected! Loads that are not ignition switch dependent are either on or off as determined by the operator - headlights, interior lights, horn, etc.
for example, my wife used to turn on her headlights when she enters her car and before she starts the car. i always warned her that in the brief millisecond/second, she can drain her battery, especially in freezing temps. sure enough, one day it happened and she stopped doing it.