Tempstar Defrost Control Board for T4H330GKB100 — 24V Heat Pump Defrost | Ships Today

Overview

This OEM defrost control board (part number 1173636) is the brain of the defrost cycle on the Tempstar T4H330GKB100 heat pump. It monitors coil temperature and run time, then initiates and terminates the defrost cycle so frost and ice cannot accumulate on the outdoor coil during heating operation. The board operates on a 24V control signal and coordinates the reversing valve, outdoor fan, and compressor during defrost. When this board fails, the heat pump can ice over solid, lose heating capacity, short-cycle, or never enter or exit defrost — symptoms that mimic a low-charge or sensor fault but trace back to the board.

Specifications

Compatibility

Directly fits the Tempstar T4H330GKB100 heat pump and is shared across many ICP-family (Heil, Comfortmaker, Tempstar) heat pumps using the 1173636 defrost board. Verify your existing board part number before ordering.

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-panel service cover.
3. Document — Photograph every wire and terminal position before disconnecting anything.
4. Remove — Unplug the low-voltage and line-voltage connectors, release the board standoffs/screws, and lift out the old defrost board.
5. Install — Seat the new board on the standoffs and reconnect every wire exactly per your photo.
6. Test — Restore power, run the unit in heating, and confirm it enters and terminates a defrost cycle correctly.

Signs You Need a Replacement

• Outdoor coil ices over and the unit never defrosts
• Unit gets stuck in defrost or defrosts far too often
• Reversing valve or outdoor fan misbehaves during heating
• Visible burnt traces, scorched relays, or no 24V output from the board

Shipping & Returns

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