Troubleshoot Heat Pumps

(ECM) Constant Airflow Motor Troubleshooting

NOTE: During testing, Motor access panel should be closed.

  • Check for 24V between R & C on ECM board.
  • Move FAN switch to ON at thermostat. Check for 24V at G & C (should be the same as R & C) terminals on ECM board. If no voltage is present from G to C, please review thermostat or thermostat wires.
  • Check High voltage at ECM motor harness circuit. If no voltage is present, ensure that high voltage is present to the unit. For 208/230V at L1 & L2 (black and white wire), for 265/277V at L1 & N (must be within 10%).
  • Check 16 pin harness connection and continuity for each wire. If there is any pin that doesn’t have continuity, change the harness.
  • On the ECM Interface board set the adjust pin to test while verifying that G to C has 24 volts. If the motor doesn’t start, replace the ECM motor. If the motor starts, replace the ECM Interface Board.