Tempstar 40VA Transformer for T9MPD050F12A4 — 115V to 24V Control Power | Ships Today

Overview

This genuine OEM control transformer (part number 1012722) supplies low-voltage power for the Tempstar T9MPD050F12A4 gas furnace. It steps 115V line voltage down to 24V at 40VA, energizing the control board, gas valve, igniter circuit, thermostat, and blower relays. A failed transformer is a leading cause of a totally dead furnace — no thermostat display, no ignition sequence, no blower. Watch for a buzzing or scorched transformer, a repeatedly blown low-voltage fuse, or zero volts across the 24V (R to C) terminals. Installing this 40VA OEM transformer restores full control-circuit power.

Specifications

Compatibility

Fits the Tempstar T9MPD050F12A4 modulating gas furnace and other ICP/Heil/Comfortmaker furnaces using a 115V-to-24V 40VA control transformer. Confirm your existing unit is rated 40VA at 115V primary before ordering.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter.
2. Access — Remove the furnace control/junction access panel.
3. Document — Photograph all primary and secondary wire connections before disconnecting.
4. Remove — Disconnect the line-voltage primary leads and 24V secondary leads, then unbolt the old transformer from its bracket.
5. Install — Mount the new transformer, reconnect primary and secondary leads per your photo, and secure all connections.
6. Test — Restore power and confirm 24V between R and C, then run a heat call to verify normal ignition.

Signs You Need a Replacement

• Furnace completely dead — blank thermostat, no ignition
• Buzzing, humming, or burnt-smelling transformer
• Repeatedly blown low-voltage (3A) fuse
• No 24V reading across the secondary terminals

Shipping & Returns

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