Tempstar Defrost Control Board for T4H348GKD100 — OEM 1173636 | Ships Today

Overview

This is a genuine OEM defrost control board (part number 1173636) for the Tempstar T4H348GKD100 heat pump. The defrost control board manages the outdoor unit's defrost sequence — monitoring coil temperature and accumulated run time, then commanding the system into and out of defrost to clear frost from the outdoor coil during heating. It also coordinates reversing-valve, compressor, and outdoor-fan timing. A failed board can leave the coil iced over, stick the unit in defrost, or cut 24V control entirely. Replacing it with the correct OEM board restores proper control logic and protects the compressor.

Specifications

Compatibility

Engineered as a direct-fit replacement for the Tempstar T4H348GKD100 heat pump condensing unit. This board is shared across the ICP / Tempstar / Heil / Comfortmaker family of heat pumps that originally shipped with part 1173636. Always confirm your existing board's part number before ordering.

Installation Guide

1. Safety First — Disconnect power at the disconnect and breaker. Verify zero voltage with a multimeter at the board terminals before touching wiring.
2. Access — Remove the outdoor unit's control-panel service cover.
3. Document — Photograph every wire and connector position on the existing board before disconnecting anything.
4. Remove — Label and unplug the low-voltage and line-voltage connectors, remove the mounting screws/standoffs, and lift out the old board.
5. Install — Mount the new board on the same standoffs and reconnect each wire exactly per your photos. Verify the defrost timing pins/jumpers match the original setting.
6. Test — Restore power and confirm the unit energizes in heating, the outdoor fan runs, and a forced/timed defrost cycle initiates correctly.

Signs You Need a Replacement

• Outdoor coil ices over and the unit never goes into defrost.
• Heat pump stuck in defrost or cycling defrost erratically.
• No 24V output to contactor / reversing valve, so the unit won't start.
• Visible scorching, burnt traces, or a failed relay on the board.

Shipping & Returns

Ships same day on orders placed before 3 PM CST. 30-day returns on unused parts in original packaging. Backed by the National HVAC Parts fitment guarantee.