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

Over the hill but still climbing.
88 Montero 2.6L auto, manual hubs, cooling fan conversion gps,recurved distributor,LSD Diff.