High RPM - No AC, Normal Idle - AC works

[jg_300_93]

93 300zx NA. A couple months ago a new issue popped up. When starting vehicle, either cold start or normal, the RPMs idle high and along with it the AC does not cool. The rpms do not go back to normal until I turn car off and on a couple times. When the rpms go back to normal, then the AC starts to cool.
I get the rpms and AC are not directly related, but this is the issue i'm facing. Mainly, what can be causing the high rpms? TIA

[VStar650CL]

Is the compressor turning on? It sounds like the ECM is activating the FICD but there's no compressor load to slow the engine. At the time the problem occurs, if the compressor clutch isn't engaging then the issue is in the clutch or the clutch circuit and not the engine controls.

[jg_300_93]

Is the compressor turning on? It sounds like the ECM is activating the FICD but there's no compressor load to slow the engine. At the time the problem occurs, if the compressor clutch isn't engaging then the issue is in the clutch or the clutch circuit and not the engine controls.

I need to check if the compressor comes on, but if I turn off the AC completely, the rpms stay the same either way.. wouldn't it get back to normal if the compressor is off?

[VStar650CL]

It should, maybe there's a problem with the ECT sensor making the ECM think the engine is hot, but first things first, see how the clutch is behaving. The lack of cooling when the problem occurs tells you something, and if the clutch isn't engaged, the next question is why. Like most Nissans from that era, your ZX has separate senders for the ECT and the temperature gauge in the dash. If the ECT is lying then it may be that the ECM thinks the engine is hot and is deliberately disabling the A/C and ramping up the idle, but because the senders are separate, your gauge won't show any problem. If the A/C relay is healthy but it isn't being turned on, that's the most likely cause.