Tempstar Defrost Control Board for T4H424GKD100 — Heat Pump Timed Defrost | Ships Today
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Overview
This OEM defrost control board (part number 1173636) is the brain of the defrost cycle in your Tempstar T4H424GKD100 heat pump. In heating mode, frost builds on the outdoor coil and chokes off airflow. The defrost board monitors the run time and the defrost thermostat, then periodically reverses the system into a brief cooling cycle to melt that ice off the coil — switching the reversing valve, stopping the outdoor fan, and energizing auxiliary heat so you don't feel a cold blast indoors. It uses a timed/temperature-terminated logic with selectable intervals. When this board fails, the heat pump either never defrosts (coil ices into a solid block and heating capacity collapses) or defrosts constantly (wasting energy and short-cycling). It also commonly governs the outdoor fan relay and the 24V control outputs, so a failure can take down more than just defrost.
Specifications
| Spec | Value |
|---|---|
| Part Number | 1173636 |
| Type | Defrost Control Board |
| Brand | Tempstar (ICP / Heil) |
| Control Voltage | 24V |
| Application | Heat Pump Outdoor Unit |
| Function | Defrost timing, reversing valve & fan control |
| Fitment | OEM Replacement |
Compatibility
Factory-specified for the Tempstar T4H424GKD100 heat pump and shared across matching ICP-family outdoor units (Heil, Comfortmaker, Arcoaire) of the same platform. Match the board's part number, terminal layout, and defrost-interval pins to your existing board before installing.
Installation Guide
- Safety First — Disconnect power at the disconnect and breaker, then verify zero voltage with a multimeter before touching the control box.
- Access — Remove the service panel and locate the defrost board in the control compartment.
- Document — Photograph every wire, plug, and the defrost-timer jumper position before disconnecting.
- Remove — Unplug the harnesses, release the mounting standoffs/screws, and lift out the old board.
- Install — Mount the new board, set the defrost interval jumper to match the original, and reconnect every harness per your photo.
- Test — Restore power, run a heating call, and initiate a forced defrost to confirm the reversing valve shifts and the fan cycles correctly.
Signs You Need a Replacement
- Outdoor coil ices over solid and never clears in heating mode.
- Heat pump defrosts far too often or short-cycles.
- No outdoor fan operation or reversing valve not switching.
- Visible burn marks, scorched traces, or a blown relay on the old board.
Shipping & Returns
Ships same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.
Shipping Information
- Orders placed before 3PM CST ship same business day
- Standard delivery: 2-5 business days
- Express shipping available at checkout
- Free shipping on orders over $75
- Tracking number emailed upon shipment
Return Policy
- 30-day returns on unused parts in original packaging
- Electrical parts (capacitors, contactors, control boards) are final sale once installed
- Email info@nationalhvacparts.com to initiate a return
- Refunds processed within 5-7 business days