Q: Fast Idle does not activate when A/C Compressor engages.

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Car idles normally at 750 rpm. However, when idling (such as at a traffic light), and the A/C Compressor engages, idle remains at 750 rpm (engine struggles) and does not advance to 1000 rpm, like it should.

My car has 70000 miles.
My car has an automatic transmission.

The idle is not supposed to increase in speed when your compressor engages, rather the throttle plate should adjust at the same time the A/C engages to maintain the same RPM at idle. This will keep the idle the same with A/C on or off. If the idle drops below 750 and then jumps real high then this is a problem and should be looked at. The throttle plate, which controls the idle speed, may need to be cleaned or inspected.

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