917178A Nordyne Defrost Control Board

Product Overview

917178A is the factory-original defrost control board for Nordyne and private-label heat pump systems. It monitors coil and ambient temperatures, initiates the defrost sequence by energizing the reversing valve and compressor, and employs a built-in 5-minute time delay to prevent rapid cycling and ensure efficient frost removal.

Cross-Reference Part Numbers

Cross-reference data sourced from internal catalogs and H & S Mobile Home Supplies2

Compatibility

• Nordyne and OEM private-label heat pumps (Intertherm, Miller, Coleman, Frigidaire, Maytag)

• Residential split-system heat pumps requiring a dedicated defrost control module

• Replaces single-stage defrost control boards in models originally using 917178, 917012 series parts4

Technician Notes

• Always disconnect all power and discharge capacitors before servicing the control board.

• Use an ESD wrist strap and handle the board by its edges to prevent static damage.

• Photograph or diagram existing wire connections and sensor locations before removal.

• Inspect defrost termination thermostat and ambient sensor for correct placement and continuity.

• Verify dip-switch or jumper settings according to the unit’s service manual for defrost timing and temperature thresholds.

• After installation, cycle the heat pump through cooling and heating modes to confirm normal operation.

• Observe the board’s LED flash codes during defrost initiation and termination; refer to the OEM manual for code definitions.

• Perform multiple defrost cycles under controlled frost load to ensure reliable performance.

Additional Resources

• Downloadable OEM wiring diagram & installation manual (PDF)

• Printable cross-reference sheet covering Nordyne and private labels

• Step-by-step video tutorial on defrost board replacement

Replacement defrost control kit for heat pumps. Includes built-in 5 minute time delay.

Replaces 917012, 917178, 621301, 621579, 624519, 624608, 624626, 624633, 1084-83-4000B & 624656.