Tempstar 40VA Transformer for T8MPV100J20A1 — 115V to 24V Control Transformer | Ships Today

Overview

This is a genuine OEM 40VA control transformer (Part No. 1012722) for the Tempstar T8MPV100J20A1 furnace. It steps line voltage of 115V down to the 24V low-voltage control circuit that powers the thermostat, gas valve, igniter relay, and control board. Without a working transformer the entire 24V control system goes dead — the furnace will not respond to a thermostat call for heat. Common failure symptoms include a completely unresponsive furnace, a blank or dead thermostat, a humming or buzzing transformer, a blown low-voltage fuse, or a visibly scorched/melted transformer body. Rated at 40VA, this transformer provides ample capacity for the control loads on this model.

Specifications

Compatibility

Engineered as a direct OEM fit for the Tempstar T8MPV100J20A1 gas furnace. This 115V-to-24V 40VA transformer is also shared across many ICP-family furnaces sold under the Tempstar, Heil, Comfortmaker, and Arcoaire brands. Always confirm your existing transformer is a 115V primary / 24V secondary 40VA unit before ordering.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter before touching any wiring.
2. Access — Remove the furnace control/blower service panel to expose the control box.
3. Document — Photograph all primary and secondary wire connections before disconnecting anything.
4. Remove — Label and disconnect the 115V primary leads and 24V secondary leads, then unbolt the failed transformer from its mounting bracket.
5. Install — Mount the new transformer, reconnect the primary and secondary wiring exactly per your photo, and confirm tight connections.
6. Test — Restore power, call for heat at the thermostat, and verify 24V on the secondary with your multimeter and normal furnace startup.

Signs You Need a Replacement

• Furnace is completely unresponsive to thermostat calls for heat.
• Thermostat screen is blank or loses power.
• Repeatedly blown low-voltage (24V) fuse on the control board.
• Transformer is hot, buzzing, swollen, or shows burn marks.

Shipping & Returns

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