{"product_id":"tempstar-40va-transformer-for-t8mpv125j20b1-115v-to-24v-ships-today","title":"Tempstar 40VA Transformer for T8MPV125J20B1 — 115V to 24V | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\n\u003cp\u003eThis is a genuine OEM control transformer (part number 1172810) for the Tempstar T8MPV125J20B1 two-stage gas furnace. It converts 115V line voltage to the 24V low-voltage power that runs the thermostat, gas valve, hot surface igniter circuit, and control board. Rated at 40VA, it has the capacity to drive every 24V load on the furnace simultaneously. A failed transformer kills the entire control system — the thermostat may go blank and the furnace will not answer a heat call even though 115V is present at the primary. Buzzing windings, an open internal thermal fuse, or a burnt-insulation smell all indicate it is time to replace the transformer.\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\u003e1172810\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eControl Transformer\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\u003eRating\u003c\/td\u003e\n\u003ctd\u003e40 VA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePrimary Voltage\u003c\/td\u003e\n\u003ctd\u003e115V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSecondary 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\u003eGas Furnace Control Circuit\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eCompatibility\u003c\/h3\u003e\n\u003cp\u003eDesigned for the Tempstar T8MPV125J20B1 furnace and interchangeable across the ICP family (Heil, Comfortmaker, Arcoaire, KeepRite) using the same 40VA 115V-to-24V control transformer. Confirm the part number on your existing transformer before ordering.\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 furnace switch and breaker, then verify zero voltage with a multimeter on the primary and secondary leads.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccess\u003c\/strong\u003e — Remove the furnace control\/blower compartment service panel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDocument\u003c\/strong\u003e — Photograph all primary and secondary wiring before disconnecting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove\u003c\/strong\u003e — Label and disconnect the line-voltage primary leads and 24V secondary leads, then unbolt the failed transformer from its bracket.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall\u003c\/strong\u003e — Mount the new transformer, reconnect leads exactly per your photo, and secure every connection.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e — Restore power and verify 24V across the secondary and normal furnace operation on a heat call.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch3\u003eSigns You Need a Replacement\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eNo 24V output while 115V is present on the primary\u003c\/li\u003e\n\u003cli\u003eDead thermostat or furnace that ignores the heat call\u003c\/li\u003e\n\u003cli\u003eBuzzing, humming, or burnt smell from the transformer\u003c\/li\u003e\n\u003cli\u003eControl fuse on the board repeatedly blows\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":63021687374195,"sku":"1172810-GEN","price":29.0,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048406237555,"sku":"1172810","price":37.7,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-transformer-control-1172810_f2b220c7-5ced-4e54-9f6c-e489cc11f2e9.jpg?v=1782958361","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-40va-transformer-for-t8mpv125j20b1-115v-to-24v-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}