Tempstar 40VA Transformer for T8MPL100F20A1 — 115V to 24V | Ships Today

Overview

This genuine OEM 40VA control transformer (OEM Part #1012722) powers the 24V control circuit of the Tempstar T8MPL100F20A1 gas furnace. It steps 115V line voltage down to 24V to supply the thermostat, gas valve, ignition control board, and relays. A failed transformer is among the most common causes of a fully dead furnace — no thermostat display, no ignition sequence, and no blower. Typical symptoms include a repeatedly blown low-voltage fuse, a burnt smell at the control board, or zero volts across the secondary 'R' and 'C' terminals.

Specifications

Compatibility

Designed for the Tempstar T8MPL100F20A1 furnace and compatible ICP/Heil/Comfortmaker furnaces using a 40VA 115V-to-24V control transformer. Verify the primary voltage tap and VA rating against the unit you are servicing.

Installation Guide

1. Safety First — Disconnect power at the service switch and verify zero voltage with a multimeter.
2. Access — Remove the furnace control-compartment service panel.
3. Document — Photograph every primary and secondary wire connection before disconnecting.
4. Remove — Label and disconnect the leads, then unbolt the failed transformer from its bracket.
5. Install — Mount the new transformer and reconnect primary (line) and secondary (24V) leads exactly per your photo.
6. Test — Restore power and confirm 24V across the secondary terminals and a normal call-for-heat sequence.

Signs You Need a Replacement

• Furnace completely dead — no thermostat power
• Repeatedly blown 3A low-voltage control fuse
• Zero or low voltage measured on the 24V secondary
• Burnt smell or discoloration at the transformer

Shipping & Returns

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