engine RPM drops when A/C turned on

[180sxfaktory]

Hello Online Mechanic! Can you explain why engine RPM drops when the A/C is turned on, instead of RPM rising? I'm looking for an electrical input signal that may be dead and not telling the ECU to raise engine RPM. Where should I start looking and what should I notice?

Thank you!

[wynnEZ]

Thats normal for it to drop. The alternator can only supply so much energy to the battery at low rpms. Same goes for your lights. Turn them on at idle and your rpm's will drop. Not a big deal.

[Silvia2b]

Maybe you have a IAA valve that is not functioning correctly and is gummed up when AC is activated it doesn't open correctly to adjust the idle? have you inspected the IAA/IACV ?

[180sxfaktory]

Thanks! I suspected it was the IACV. I checked it against a known good one and idle RPM raised when I turned on the A/C, so I cleaned the IACV with thinner and low pressure air dried it. It is fixed now. Again, thanks!

[Silvia2b]

Great, glad you got it fixed!