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Home >> GMC >> 1983 >> Forward Control 5.7 M, Automatic, 475/M40 >> Repair and Diagnosis (Single Page) >> Engine Performance >> Adjustment >> Tune-Up - 5.0L V8 VIN [H] >> Hot (Slow) Idle Rpm >> A/C Idle Speed Solenoid (ISS) Functional Check

A/C Idle Speed Solenoid (ISS) Functional Check

NOTE: Not all models have an ISS.
  1. Turn on the ignition, but do not start the engine. Turn the A/C to ON position. Open the throttle to allow the solenoid to extend, then close the throttle. Disconnect the lead at the solenoid. The solenoid plunger should drop away from the throttle lever.
  2. Connect the solenoid lead. The plunger should move out and contact the throttle lever. The solenoid may not be strong enough to open the throttle, but the plunger should move.
  3. If the plunger does not move in and out when the lead is disconnected and connected, insert a test light between the solenoid feed wire and ground. If the light lights, replaced the solenoid. If the light does not light, locate the cause of the open circuit solenoid feed wire.
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