{"product_id":"tempstar-40va-transformer-for-t8mpt100j20a1-115v-to-24v-control-power-ships-today","title":"Tempstar 40VA Transformer for T8MPT100J20A1 — 115V to 24V Control Power | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\n\u003cp\u003eThis OEM control transformer (Part #1012722) supplies the low-voltage power that runs your Tempstar T8MPT100J20A1 furnace's control circuit. It steps incoming 115-volt line power down to 24 volts at 40VA, energizing the control board, thermostat, gas valve, igniter circuit, and blower relays. Without a healthy transformer the entire low-voltage side of the furnace goes dead — no thermostat response, no call for heat, and no fan operation. A transformer typically fails from a shorted secondary winding, an overloaded 24V circuit, a nearby lightning surge, or simple age-related insulation breakdown. Common symptoms include a completely unresponsive thermostat, a blank control board, repeatedly blown low-voltage fuses, or a faint burning-electrical smell at the furnace. This is a direct OEM replacement rated to the exact 40VA load of your equipment.\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\u003eStep-Down Control 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\u003e40 VA\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 for the Tempstar T8MPT100J20A1 gas furnace. This same 115V-to-24V 40VA transformer is shared across many ICP-family furnaces (Tempstar, Heil, Comfortmaker, Arcoaire) of the same vintage. Always confirm the original part number and the primary\/secondary voltage stamped on your existing transformer 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 at the transformer terminals.\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 every wire on the primary (line) and secondary (24V) terminals before disconnecting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove\u003c\/strong\u003e — Disconnect the primary and secondary leads, then unbolt the transformer from its mounting bracket.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall\u003c\/strong\u003e — Mount the new transformer, reconnect primary leads to line voltage and secondary leads to the 24V circuit exactly per your photo.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e — Restore power, confirm 24V across the secondary, and verify the thermostat calls for heat and the board powers up.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch3\u003eSigns You Need a Replacement\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eThermostat is completely dead or display is blank.\u003c\/li\u003e\n\u003cli\u003eControl board shows no power and the furnace won't start a heat cycle.\u003c\/li\u003e\n\u003cli\u003eLow-voltage fuse blows immediately or repeatedly.\u003c\/li\u003e\n\u003cli\u003eBurning smell or discoloration at the transformer body.\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":63021717455219,"sku":"1012722-GEN","price":32.0,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048405418355,"sku":"1012722","price":41.6,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-transformer-control-1012722_84357afb-1946-498c-aecc-098f504ca793.jpg?v=1782958329","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-40va-transformer-for-t8mpt100j20a1-115v-to-24v-control-power-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}