Tempstar Control Transformer for TDE125J20G1 — 40VA 115V to 24V | Ships Today

Overview

This OEM Tempstar control transformer (part #1012722) steps 115V line voltage down to 24V to power the low-voltage control circuit of your furnace or air handler. Rated at 40VA, it supplies the thermostat, gas valve, relays, and control board. When a transformer fails, the entire 24V control system goes dead — the thermostat screen goes blank, the furnace won't fire, and you may smell a burnt or acrid odor near the control box. A buzzing transformer or a tripped low-voltage fuse on the board are also common warning signs of a failing unit.

Specifications

Compatibility

Engineered as a direct OEM replacement for the Tempstar TDE125J20G1 gas furnace. Also fits many Heil, Comfortmaker, and ICP-family units that use the 1012722 transformer. Always verify the part number on your existing transformer before ordering.

Installation Guide

1. Safety First — Disconnect power at the breaker and verify zero voltage at the unit with a multimeter.
2. Access — Remove the furnace control panel to expose the transformer.
3. Document — Photograph the primary and secondary wiring before disconnecting anything.
4. Remove — Disconnect the 115V primary leads and the 24V secondary leads, then unbolt the transformer from its bracket.
5. Install — Mount the new transformer and reconnect each lead exactly per your photo.
6. Test — Restore power and confirm 24V across the secondary terminals and normal control operation.

Signs You Need a Replacement

• Blank thermostat and dead 24V control circuit
• Repeatedly blown low-voltage control board fuse
• Audible buzzing or humming from the transformer
• Burnt smell or visible scorching on the windings

Shipping & Returns

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