{"product_id":"tempstar-40va-transformer-for-t8mpn100j20b1-115v-to-24v-ships-today","title":"Tempstar 40VA Transformer for T8MPN100J20B1 — 115V to 24V | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\n\u003cp\u003eThis genuine OEM 40VA control transformer (part number 1172810, \"TRANS 115\u0026gt;24 40VA\") supplies the 24-volt control power for the Tempstar T8MPN100J20B1 gas furnace. It steps the 115-volt line voltage down to 24 volts AC to run the thermostat, gas valve, control board relays, and blower\/fan circuits. A failed transformer is one of the most common causes of a completely dead furnace: no display, no thermostat response, and no blower or ignition. Typical failure symptoms include a buzzing or burnt-smelling transformer, repeatedly blown low-voltage fuses, intermittent 24V, or zero output on the secondary even with 115V present on the primary.\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\u003eDescription\u003c\/td\u003e\n\u003ctd\u003eTransformer, 115V \u0026gt; 24V, 40VA\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 family)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePrimary Voltage\u003c\/td\u003e\n\u003ctd\u003e115V AC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSecondary Voltage\u003c\/td\u003e\n\u003ctd\u003e24V AC\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\u003eFitment\u003c\/td\u003e\n\u003ctd\u003eOEM — exact 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\u003eBuilt for the Tempstar T8MPN100J20B1 100,000 BTU gas furnace and shared across many ICP \/ Heil \/ Comfortmaker furnaces that use a 40VA 115-to-24V control transformer. Confirm your existing transformer is rated 40VA with a 115V primary and 24V secondary before ordering. This is a direct OEM replacement for 1172810.\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 at the transformer leads with a multimeter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccess\u003c\/strong\u003e — Remove the furnace control-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, remove the transformer mounting screws, and lift out the old transformer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall\u003c\/strong\u003e — Mount the new transformer, reconnect the 115V primary and 24V secondary leads exactly per your photo, and secure all connections.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e — Restore power and verify 24V AC across the secondary and normal thermostat, ignition, and blower operation.\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 dead — no thermostat response or blower\u003c\/li\u003e\n\u003cli\u003eRepeatedly blown 3A or 5A low-voltage control fuse\u003c\/li\u003e\n\u003cli\u003eTransformer buzzing, overheating, or smelling burnt\u003c\/li\u003e\n\u003cli\u003e115V present on the primary but no 24V on the secondary\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":63021764215155,"sku":"1172810-GEN","price":28.95,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048404664691,"sku":"1172810","price":37.63,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-transformer-control-1172810_289274f6-a413-4698-b2f2-2b4e20dcb4ea.jpg?v=1782958300","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-40va-transformer-for-t8mpn100j20b1-115v-to-24v-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}