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Home › Pontiac › 1991 › LeMans Base › Repair and Diagnosis (Single Page) › Heating, Ventilation & A/C (HVAC) › HVAC Control Systems › A/C-Heater System - Manual › Testing › A/C Control Relay Test › Compressor Control

Compressor Control

  1. Disconnect A/C control relay connector. Start engine and allow to idle. Set air control knob to NORMAL position.
  2. Measure voltage between Red/White/Black wire of A/C control relay connector and ground. If battery voltage does not exist, check for open circuit in Red/White/Black wire or blown fuse No. 13. If battery voltage exists, go to next step.
  3. Measure voltage between Red/Yellow wire of A/C control relay connector and ground. If battery voltage does not exist, check Red/Yellow wire for open circuit. If battery voltage exists, go to next step.
  4. Measure voltage between Red/White/Black and Black wires of A/C control relay connector. If battery voltage does not exist, check Black wire for open circuit between A/C control relay and charge (charging system) relay.
  5. If wire is okay, disconnect charge relay. Measure voltage between Black wire of relay connector and ground. If battery voltage does not exist, check Black wire for open or short circuit. If battery voltage exists, replace charge relay.
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