Tempstar Defrost Control Board for T4H424GKB100 — OEM Heat Pump Board | Ships Today

Overview

This genuine OEM defrost control board (part #1173636) is the logic center of the Tempstar T4H424GKB100 heat pump's defrost cycle. In heating mode, frost builds on the outdoor coil and must be periodically melted off so the unit can keep absorbing heat. The defrost board monitors the defrost thermostat and elapsed run time, then initiates a defrost cycle by reversing the valve, shutting off the outdoor fan, and energizing the cycle until the coil clears. When this board fails, the heat pump can ice over solid in winter, fail to switch the reversing valve, run auxiliary heat constantly, or lock out entirely.

Specifications

Compatibility

Direct OEM replacement for the Tempstar T4H424GKB100 heat pump. ICP-family defrost boards are shared across Heil, Comfortmaker, and Tempstar outdoor units of the same generation. Match the OEM part number 1173636 and the board's terminal layout to your existing board 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 outdoor unit control box / electrical access panel.
3. Document — Photograph every wire and terminal connection on the existing board.
4. Remove — Unplug the harnesses, release the board standoffs, and lift out the old board.
5. Install — Seat the new board on the standoffs and reconnect each harness exactly per your photo.
6. Test — Restore power and confirm normal heating/cooling operation and a clean defrost cycle.

Signs You Need a Replacement

• Outdoor coil freezes over and never defrosts in heating mode
• Reversing valve fails to switch between heat and cool
• Auxiliary/emergency heat runs constantly
• Unit locks out or behaves erratically during defrost

Shipping & Returns

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