{"product_id":"tempstar-defrost-control-board-for-t4h418gka100-heat-pump-ships-today","title":"Tempstar Defrost Control Board for T4H418GKA100 — Heat Pump | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\u003cp\u003eThis OEM defrost control board (part 1173636) is the electronic brain that manages the defrost cycle on the Tempstar T4H418GKA100 heat pump. In heating mode, frost accumulates on the outdoor coil; the defrost board monitors time and coil temperature (via the defrost sensor), then periodically reverses the system to melt that frost — energizing the reversing valve, shutting the outdoor fan, and bringing on auxiliary heat to temper the supply air. When this board fails, the heat pump can ice over completely, lose heating capacity, short-cycle, or run constant emergency heat and spike the electric bill. Because it controls the reversing valve and fan relays, a failed board often presents as multiple unrelated-looking symptoms at once.\u003c\/p\u003e\u003ch3\u003eSpecifications\u003c\/h3\u003e\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\u003eOEM Part 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\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\u003eApplication\u003c\/td\u003e\n\u003ctd\u003eHeat Pump Outdoor Unit\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch3\u003eCompatibility\u003c\/h3\u003e\u003cp\u003eBuilt for the Tempstar T4H418GKA100 heat pump and shared ICP\/Heil\/Comfortmaker platforms using the 1173636 defrost board. Confirm the part number printed on your existing board and match the connector layout before installing.\u003c\/p\u003e\u003ch3\u003eInstallation Guide\u003c\/h3\u003e\u003col\u003e\n\u003cli\u003e\n\u003cstrong\u003eSafety First\u003c\/strong\u003e — Disconnect power at the breaker and outdoor disconnect; verify zero voltage with a multimeter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccess\u003c\/strong\u003e — Remove the control compartment access panel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDocument\u003c\/strong\u003e — Photograph every plug and wire location on the existing board before touching anything.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove\u003c\/strong\u003e — Unplug each connector, release the board standoffs or screws, and lift out the failed board.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall\u003c\/strong\u003e — Mount the new board and transfer each connector to the matching terminal per your photo, including the defrost sensor lead.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e — Restore power and initiate a forced\/test defrost to confirm the valve, fan, and aux-heat outputs sequence correctly.\u003c\/li\u003e\n\u003c\/ol\u003e\u003ch3\u003eSigns You Need a Replacement\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eOutdoor coil ices over and the unit never defrosts\u003c\/li\u003e\n\u003cli\u003eHeat pump stuck running auxiliary\/emergency heat\u003c\/li\u003e\n\u003cli\u003eDefrost cycles too often or never initiates\u003c\/li\u003e\n\u003cli\u003eNo response from reversing valve or outdoor fan during defrost\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eShipping \u0026amp; Returns\u003c\/h3\u003e\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":63021790560627,"sku":"1173636-GEN","price":145.0,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048442937715,"sku":"1173636","price":188.5,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-control-board-defrost-1173636_7f583dce-0be9-4c52-ab29-edfa79810d21.jpg?v=1782959777","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-defrost-control-board-for-t4h418gka100-heat-pump-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}