{"product_id":"tempstar-40va-transformer-for-t9mpx080j12a2-115v-to-24v-ships-today","title":"Tempstar 40VA Transformer for T9MPX080J12A2 — 115V to 24V | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\u003cp\u003eThis OEM control transformer (part 1172810) steps line voltage down from 115V to 24V to power the low-voltage control circuit in your Tempstar T9MPX080J12A2 gas furnace. Rated at 40VA, it supplies the thermostat, control board, gas valve, and relays. When a transformer fails — usually from a shorted thermostat wire, a stuck contactor, or simple age — the entire 24V control system goes dead: no thermostat display, no blower, no heat. Many transformers include a resettable or replaceable secondary fuse; replacing the whole transformer is the reliable fix when the windings are open or burned.\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\u003e1172810\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eControl \/ Step-Down 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\u003e115 VAC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSecondary Voltage\u003c\/td\u003e\n\u003ctd\u003e24 VAC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApplication\u003c\/td\u003e\n\u003ctd\u003eFurnace Control Circuit\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch3\u003eCompatibility\u003c\/h3\u003e\u003cp\u003eDirect-fit replacement for the Tempstar T9MPX080J12A2 modulating gas furnace. The 1172810 40VA transformer is widely used across ICP, Heil, Comfortmaker, and Carrier-family furnaces and air handlers running the same control platform. Confirm your existing unit is rated 115V primary \/ 24V secondary at 40VA 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 furnace switch and breaker, then verify zero voltage at the transformer leads with a multimeter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccess\u003c\/strong\u003e — Remove the control compartment service panel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDocument\u003c\/strong\u003e — Photograph the primary and secondary wiring before disconnecting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove\u003c\/strong\u003e — Label and disconnect the leads, remove the transformer mounting screws, and pull the old unit.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall\u003c\/strong\u003e — Mount the new transformer and reconnect the 115V primary and 24V secondary leads exactly as documented.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e — Restore power, confirm 24V at the secondary with a meter, and verify the thermostat and control board power up.\u003c\/li\u003e\n\u003c\/ol\u003e\u003ch3\u003eSigns You Need a Replacement\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eBlank or dead thermostat with good batteries\u003c\/li\u003e\n\u003cli\u003eNo 24V output measured at the secondary terminals\u003c\/li\u003e\n\u003cli\u003eBurning smell or visibly charred transformer windings\u003c\/li\u003e\n\u003cli\u003eFurnace completely unresponsive to a heat call\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eShipping \u0026amp; Returns\u003c\/h3\u003e\u003cp\u003eShips same day on orders placed before 3 PM CST. 30-day hassle-free returns. Backed by the National HVAC Parts fitment guarantee.\u003c\/p\u003e","brand":"Tempstar","offers":[{"title":"Direct Replacement","offer_id":63021678133619,"sku":"1172810-GEN","price":29.95,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048408170867,"sku":"1172810","price":38.94,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-transformer-control-1172810_235edb50-40f2-40b9-94bd-40182ae4ca9f.jpg?v=1782958439","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-40va-transformer-for-t9mpx080j12a2-115v-to-24v-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}