Tempstar Transformer for T9MPV100J20C1 — 115V to 24V 40VA | Ships Today

Overview

This OEM control transformer (part #1172810) steps line voltage down from 115V to 24V for the low-voltage control circuit of your Tempstar T9MPV100J20C1 gas furnace. Rated at 40VA, it supplies stable, clean 24VAC power to the integrated furnace control board, thermostat, gas valve, igniter circuit, and safety switches. When a control transformer fails, the entire 24V control system goes dead — the furnace will not respond to a thermostat call, the control board shows no power, and nothing energizes. Common causes of failure are a shorted secondary winding, an overloaded control circuit, a nearby lightning surge, or simple age-related winding breakdown. Installing the correct 40VA OEM transformer restores full control power and protects downstream components from voltage irregularities.

Specifications

Compatibility

Designed as a direct-fit replacement for the Tempstar T9MPV100J20C1 modulating variable-speed gas furnace. This 115V-to-24V 40VA transformer is also used across many ICP-family furnaces (Tempstar, Heil, Comfortmaker, Arcoaire) that share the same control-power requirement. Always confirm your existing transformer is rated 115V primary / 24V secondary at 40VA before installing.

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 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 failed transformer from its mounting bracket.
5. Install — Mount the new transformer, reconnect the 115V primary and 24V secondary leads exactly per your photo.
6. Test — Restore power, confirm 24VAC at the secondary with a meter, and verify the furnace responds to a thermostat call.

Signs You Need a Replacement

• Furnace completely unresponsive to thermostat calls with no control-board lights.
• No 24VAC measured at the transformer secondary terminals.
• Repeated blown low-voltage fuse on the control board.
• Burnt smell or visibly scorched transformer housing.

Shipping & Returns

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