Tempstar Defrost Control Board for T4H548GKA100 — OEM 1173636 Heat Pump Control | Ships Today

Overview

The Tempstar defrost control board (OEM part #1173636) is the brain of the defrost cycle on your T4H548GKA100 heat pump. It monitors coil temperature and run time, then commands the unit into and out of defrost so frost and ice never choke the outdoor coil during heating season. When this board fails, the heat pump may ice over solid, run defrost endlessly, never defrost at all, or fail to switch the reversing valve and auxiliary heat at the right time. Replacing the defrost board restores correct timed/temperature-initiated defrost and protects the compressor from liquid slugging.

Specifications

Compatibility

Engineered for the Tempstar T4H548GKA100 heat pump and shared across many ICP-family outdoor units (Tempstar, Heil, Comfortmaker, Arcoaire). Always verify the existing board part number before ordering.

Installation Guide

1. Safety First — Disconnect power at the disconnect and breaker; verify zero voltage with a multimeter.
2. Access — Remove the outdoor unit control/access panel.
3. Document — Photograph every wire and connector position before disconnecting.
4. Remove — Unplug low-voltage harnesses and line-voltage terminals, then unscrew the old defrost board from its standoffs.
5. Install — Mount the new board, transfer the defrost timing jumper to the same pin setting, and reconnect every wire per your photo.
6. Test — Restore power, force a defrost cycle, and confirm the reversing valve and fan respond correctly.

Signs You Need a Replacement

• Outdoor coil freezes solid in heating mode
• Unit runs defrost constantly or never defrosts
• No 24V output to reversing valve or fan during defrost
• Visible burn marks, corrosion, or scorched relays on the board

Shipping & Returns

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