Tempstar Defrost Control Board for T4H318GKD100 — Heat Pump Timed/Demand Defrost | Ships Today

Overview

The OEM defrost control board (part #1173636) is the brain of the defrost cycle on your Tempstar T4H318GKD100 heat pump. It monitors coil temperature and accumulated run time, then commands the reversing valve, outdoor fan, and auxiliary heat to clear frost from the outdoor coil during cold weather. A failed board is one of the most common causes of a heat pump that ices over, fails to defrost, won't switch between heating and cooling, or short-cycles. The board operates on a 24V control signal and integrates the defrost sensor, timer logic, and relay outputs into a single replaceable assembly.

Specifications

Compatibility

Designed as the factory replacement for the Tempstar T4H318GKD100 heat pump condenser. This board is shared across many ICP-family heat pumps (Tempstar, Heil, Comfortmaker, Arcoaire) of the same vintage — verify the original part number 1173636 before ordering.

Installation Guide

1. Safety First — Disconnect power at the outdoor disconnect and verify zero voltage with a multimeter.
2. Access — Remove the control panel cover from the condensing unit.
3. Document — Photograph every wire and terminal position before disconnecting anything.
4. Remove — Label and unplug the low-voltage connectors and sensor leads, then unscrew the old board from its standoffs.
5. Install — Mount the new board, reconnect each wire exactly per your photos, and seat the defrost sensor on the coil.
6. Test — Restore power and force a defrost test to confirm the reversing valve and fan respond correctly.

Signs You Need a Replacement

• Outdoor unit ices over and never defrosts
• Heat pump won't switch between heating and cooling modes
• No 24V output to the reversing valve or contactor
• 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.