Tempstar 40VA Transformer for T9MPV050F12C1 — 115V to 24V | Ships Today

Overview

This is an OEM control transformer (part number 1172810) for the Tempstar T9MPV050F12C1 gas furnace. The transformer steps down 115V line voltage to the 24V control voltage used by the thermostat, igniter circuit, gas valve, and blower controls. Rated at 40VA, it supplies the low-voltage power that runs your furnace's safety and sequencing circuits. When a transformer fails, the entire low-voltage control side goes dead: the thermostat screen blanks out, the furnace won't respond to a heat call, and you may smell a burnt-electrical odor or find a blown low-voltage fuse on the control board. A shorted thermostat wire or a failed contactor coil can overload and burn out the transformer, so inspect downstream wiring before installing the replacement.

Specifications

Compatibility

Designed as the factory transformer for the Tempstar T9MPV050F12C1 variable-speed gas furnace. This part is shared across many ICP-family furnaces (Tempstar, Heil, Comfortmaker) that use a 115V-to-24V 40VA control transformer. Confirm your existing transformer is marked 115V primary / 24V secondary / 40VA 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/blower access panel.
3. Document — Photograph all primary and secondary wire connections before disconnecting.
4. Remove — Disconnect the 115V primary leads and 24V secondary leads, then unbolt the transformer from its bracket.
5. Install — Mount the new transformer, reconnect primary and secondary leads per your photo, matching wire colors.
6. Test — Restore power, confirm 24V across the secondary terminals, and verify the furnace responds to a heat call.

Signs You Need a Replacement

• Thermostat is blank or dead with no 24V control power
• Furnace does not respond to any heat call
• Repeatedly blown low-voltage fuse on the control board
• Burnt-electrical smell or visible scorching on the transformer body

Shipping & Returns

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