Tempstar Transformer for T8MPN075B12A1 — 40VA 115V to 24V | Ships Today

Overview

This is a genuine OEM 40VA control transformer (part number 1012722) for the Tempstar T8MPN075B12A1 gas furnace. It converts incoming 115V line voltage down to the 24V low-voltage power that runs the thermostat, gas valve, ignition control, and board relays. The 40VA rating supplies enough capacity to drive every 24V load on the furnace at once. A transformer that fails — from a shorted secondary, a control-circuit overload, or age-related winding breakdown — kills control power entirely: the thermostat goes blank, ignition never starts, and the blower won't run. Replacing it with the correct OEM transformer restores stable control voltage and proper furnace operation.

Specifications

Compatibility

Designed as the factory transformer for the Tempstar T8MPN075B12A1 and shared across related ICP/Heil/Tempstar gas furnace platforms using the same 40VA, 115-to-24V control system. Verify the printed part number on your existing transformer before ordering.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter at the transformer terminals.
2. Access — Remove the furnace control/blower compartment service panel.
3. Document — Photograph all primary (line) and secondary (24V) wire connections before disconnecting.
4. Remove — Disconnect the primary and secondary leads, then unbolt the transformer from its bracket.
5. Install — Mount the new transformer, reconnect the 115V primary and 24V secondary leads per your photo, and confirm tight terminals.
6. Test — Restore power, measure 24V across the secondary, and run a full heating cycle to confirm ignition and blower operation.

Signs You Need a Replacement

• Furnace is completely dead — no thermostat display or response to a heat call.
• Low-voltage control fuse blows repeatedly.
• No 24V reading across the secondary while 115V is present at the primary.
• Buzzing, overheating, or a burnt smell from the transformer.

Shipping & Returns

Ships same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.