{"product_id":"tempstar-transformer-for-t9mpv100j20a3-115v-to-24v-40va-ships-today","title":"Tempstar Transformer for T9MPV100J20A3 — 115V to 24V 40VA | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\n\u003cp\u003eThis OEM control transformer (part #1012722) steps 115V line voltage down to 24V for the low-voltage control circuit of the Tempstar T9MPV100J20A3 gas furnace. Rated at 40VA, it supplies stable 24VAC to the integrated furnace control board, thermostat, gas valve, and safety circuits. A failed transformer kills the entire 24V control system — the furnace stops responding to thermostat calls, the control board goes dark, and nothing energizes. Common failure modes include a shorted secondary winding, an overloaded control circuit, a voltage surge, or age-related winding breakdown. Replacing it with the correct 40VA OEM transformer restores control power and protects downstream components from voltage irregularities.\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\u003e1012722\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\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\u003eRating\u003c\/td\u003e\n\u003ctd\u003e40VA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFit\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\u003eDesigned as a direct-fit replacement for the Tempstar T9MPV100J20A3 modulating variable-speed gas furnace. This 115V-to-24V 40VA transformer is common across ICP-family furnaces (Tempstar, Heil, Comfortmaker, Arcoaire) sharing the same control-power requirement. Confirm your existing unit is rated 115V primary \/ 24V secondary at 40VA 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 furnace switch and breaker, then verify zero voltage with a multimeter.\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 (line) and secondary (24V) wire connections before disconnecting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove\u003c\/strong\u003e — Disconnect the primary and 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 and reconnect the 115V primary and 24V secondary leads exactly per your photo.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e — Restore power, confirm 24VAC at the secondary with a meter, and verify the furnace responds to a thermostat call.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch3\u003eSigns You Need a Replacement\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eFurnace completely unresponsive with no control-board lights.\u003c\/li\u003e\n\u003cli\u003eNo 24VAC measured at the transformer secondary terminals.\u003c\/li\u003e\n\u003cli\u003eRepeatedly blown low-voltage fuse on the control board.\u003c\/li\u003e\n\u003cli\u003eBurnt smell or scorched transformer housing.\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":63021678985587,"sku":"1012722-GEN","price":26.95,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048490713459,"sku":"1012722","price":35.04,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-transformer-control-1012722_53db5e8f-89e2-44fb-a174-483c0e780ce3.jpg?v=1782961447","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-transformer-for-t9mpv100j20a3-115v-to-24v-40va-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}