I've read many times how the IAC motor helps keep idle RPMs up when the air conditioning is on... and figured mine was always dead (have cleaned it to no avail) as the A/C always brought RPMs down.

Well, recent tinkered made me aware of the power steering pressure switch, which DOES raise my RPM by about 200 whenever the wheel is turned hard at a stop. So, is the IAC involved in this process? Does this mean mine works? If so, what lets the ECU know that the A/C is on? Is it hard-wired somewhere/somehow? Just wondering if I should be looking for a failed sensor or disconnected wire.

Thanks for any help in understanding how this works.

Bryan
Dallas, TX
Gen I 4-door 3.0 V6

Yes, the idle speed shoud increase to compensate for AC load. When the ECU sees the imput from the AC temp switch, it should provide a ground to the AC compressor relay and increase idle speed. The same thing occurs with the P/S which pulls 8 volts to ground in the ECU ( when pressures are high) and the ECU will increase idle speed. The same thing should occur when the transmission is placed in drive.
Conner

Thanks for the info! Seeing as how I do get increased RPMs with the steering pressure and drive selection... I'm going to test the A/C temp switch and relay ground before I spend money on a new IAC.

Bryan

That's good to know, conner. How does the ecu know? shift sector switch?

Yes Ed, or what Mitsubishi likes to call the "inhibitor switch."
Conner

So if I hotwire the inhibitor switch so I can crank the truck in whatever gear I want to, the idle will stay high all the time (like it does now anyway with a no-go ISC)?

Ed: We were discussing the 3.0 engine here. I am assuming that you are using the Starion system on yours. It may well work the same however i dont have a wiring schematic handy to see where that input comes from. I will try to find one and get back.
Conner