Originally Posted by cal1320
What it comes down to is this. Will your engine tolerate a +- 200 rpm drop when at idle speed. My little 283 doesn't. I use a solenoid to hold the idle up when the air is on. The down side of the solenoid is when the air kicks on at idle, the rpm's drop until I give it a little gas. Then the solenoid will hold the new idle speed until the compressor shuts off. The solenoids wont open the throttle up on their own, they just wont let the throttle close completely when they're on. Edelbrock and most parts stores sell them for around $50-$60, or hit the junk yard for $5.
The whole point of the idle air control motor on the throttle body is that you don't need the solenoid. The idle speed is kept constant by the ECU. The added A/C sense wire just lets the ECU know it needs to temporarily bump up the idle speed.