VX Idle with A/C On
 

My VX just started idling funny when the A/C is on. When the engine cooling fa kicks on, it runs fine. When the cooling fan kicks off, it idles erratically (bounces between 1,000-1,500 RPM or so. It only does this with the A/C on (or at least that's the only time I've noticed it).

Any ideas?

The cooling fan does not draw much current so should not affect the engine rpm provided the electrical load overall is not high (headlights on, car stereo on, etc.)

The rpm should increase when the A/C compressor clutch engages which puts a load on the engine via its drive belt. On my VX, the rpm increases from 600 to 900 at this time.

Sounds like you have an idle air control valve issue since the rpm should never bounce.

That's kind of what I was thinking. I've just never heard of it being a "conditional" problem (i.e. it only happens when the A/C is on and the cooling fan is off).

what is the idle speed with the A/C off?

I remember reading another thread like this. Problem turned out to be his map sensor.