{"product_id":"tempstar-defrost-control-board-for-t4h424gkd100-heat-pump-timed-defrost-ships-today","title":"Tempstar Defrost Control Board for T4H424GKD100 — Heat Pump Timed Defrost | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\n\u003cp\u003eThis 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.\u003c\/p\u003e\n\n\u003ch3\u003eSpecifications\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpec\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003ePart Number\u003c\/td\u003e\n\u003ctd\u003e1173636\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eDefrost Control Board\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eTempstar (ICP \/ Heil)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eControl Voltage\u003c\/td\u003e\n\u003ctd\u003e24V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApplication\u003c\/td\u003e\n\u003ctd\u003eHeat Pump Outdoor Unit\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFunction\u003c\/td\u003e\n\u003ctd\u003eDefrost timing, reversing valve \u0026amp; fan control\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFitment\u003c\/td\u003e\n\u003ctd\u003eOEM Replacement\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eCompatibility\u003c\/h3\u003e\n\u003cp\u003eFactory-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.\u003c\/p\u003e\n\n\u003ch3\u003eInstallation Guide\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cstrong\u003eSafety First\u003c\/strong\u003e — Disconnect power at the disconnect and breaker, then verify zero voltage with a multimeter before touching the control box.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccess\u003c\/strong\u003e — Remove the service panel and locate the defrost board in the control compartment.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDocument\u003c\/strong\u003e — Photograph every wire, plug, and the defrost-timer jumper position before disconnecting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove\u003c\/strong\u003e — Unplug the harnesses, release the mounting standoffs\/screws, and lift out the old board.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall\u003c\/strong\u003e — Mount the new board, set the defrost interval jumper to match the original, and reconnect every harness per your photo.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e — Restore power, run a heating call, and initiate a forced defrost to confirm the reversing valve shifts and the fan cycles correctly.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch3\u003eSigns You Need a Replacement\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eOutdoor coil ices over solid and never clears in heating mode.\u003c\/li\u003e\n\u003cli\u003eHeat pump defrosts far too often or short-cycles.\u003c\/li\u003e\n\u003cli\u003eNo outdoor fan operation or reversing valve not switching.\u003c\/li\u003e\n\u003cli\u003eVisible burn marks, scorched traces, or a blown relay on the old board.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eShipping \u0026amp; Returns\u003c\/h3\u003e\n\u003cp\u003eShips same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.\u003c\/p\u003e","brand":"Tempstar","offers":[{"title":"Direct Replacement","offer_id":63021787578739,"sku":"1173636-GEN","price":169.95,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048443560307,"sku":"1173636","price":220.94,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-control-board-defrost-1173636_43257ac1-ca88-46e2-9248-186527e7b7c5.jpg?v=1782959804","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-defrost-control-board-for-t4h424gkd100-heat-pump-timed-defrost-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}