Tempstar Defrost Control Board for T4H318GKA100 — Heat Pump Timer Board | Ships Today

Overview

This genuine OEM defrost control board (Tempstar part 1173636) is the brain of the heat pump's defrost cycle. In heating mode the outdoor coil collects frost; the defrost board monitors the defrost thermostat and a timing interval, then briefly reverses the valve and shuts off the outdoor fan to melt accumulated ice before returning to heat. A failed defrost board leaves the outdoor coil iced over, kills heating capacity, and can trip the system on high head pressure. Typical failure symptoms include a coil that ices up solid in winter, defrost cycles that never run or run constantly, the auxiliary heat staying engaged, or the outdoor fan behaving erratically.

Specifications

Compatibility

Direct-fit replacement for the Tempstar T4H318GKA100 heat pump and shared-platform ICP, Heil, and Comfortmaker outdoor units that use the same defrost control board. Match the board part number and connector layout before installing.

Installation Guide

1. Safety First — Disconnect power at the disconnect and breaker, then verify zero voltage with a multimeter.
2. Access — Remove the condenser control-box panel to reach the board.
3. Document — Photograph every plug and wire location before unplugging anything.
4. Remove — Disconnect the harness plugs and low-voltage leads, then unclip or unscrew the board from its standoffs.
5. Install — Mount the new board, reseat each connector firmly, and confirm the defrost timing pins match the old board.
6. Test — Restore power, run a heating call, and verify normal operation and a forced defrost if accessible.

Signs You Need a Replacement

• Outdoor coil ices over and stays frozen in heating mode.
• Defrost cycle never initiates or runs continuously.
• Auxiliary/emergency heat runs constantly.
• Outdoor fan or reversing valve behaves erratically during heat.

Shipping & Returns

Ships same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.