Tempstar Transformer for T9MPV100J20A3 — 115V to 24V 40VA | Ships Today

Overview

This OEM control transformer (part #1012722) steps 115V line voltage down to 24V for the low-voltage control circuit of the Tempstar T9MPV100J20A3 gas furnace. Rated at 40VA, it supplies stable 24VAC to the integrated furnace control board, thermostat, gas valve, and safety circuits. A failed transformer kills the entire 24V control system — the furnace stops responding to thermostat calls, the control board goes dark, and nothing energizes. Common failure modes include a shorted secondary winding, an overloaded control circuit, a voltage surge, or age-related winding breakdown. Replacing it with the correct 40VA OEM transformer restores control power and protects downstream components from voltage irregularities.

Specifications

Compatibility

Designed as a direct-fit replacement for the Tempstar T9MPV100J20A3 modulating variable-speed gas furnace. This 115V-to-24V 40VA transformer is common across ICP-family furnaces (Tempstar, Heil, Comfortmaker, Arcoaire) sharing the same control-power requirement. Confirm your existing unit 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 bracket.
5. Install — Mount the new transformer and 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 with no control-board lights.
• No 24VAC measured at the transformer secondary terminals.
• Repeatedly blown low-voltage fuse on the control board.
• Burnt smell or scorched transformer housing.

Shipping & Returns

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