Tempstar 40VA Transformer for T9MPV100J20A2 — 115V to 24V | Ships Today

Overview

This OEM control transformer (part 1012722) steps the 115V line voltage down to the 24V control voltage used by the Tempstar T9MPV100J20A2 furnace. Rated at 40VA, it powers the control board, thermostat, gas valve, and low-voltage relays. When a transformer fails, the entire low-voltage control circuit goes dead — the thermostat screen may go blank, the furnace won't respond to a heat call, and you'll read 0V where 24V is expected. Transformers commonly fail from a shorted control wire, a stuck contactor, or simple age-related winding breakdown. This direct-fit replacement restores stable 24V control power.

Specifications

Compatibility

Built for the Tempstar T9MPV100J20A2 gas furnace and compatible ICP / Heil / Comfortmaker units that use part 1012722. Confirm your model and original transformer rating before ordering.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker and verify zero voltage with a multimeter.
2. Access — Remove the control/electrical compartment service panel.
3. Document — Photograph all primary and secondary wire connections before disconnecting.
4. Remove — Disconnect the wire leads and remove the transformer mounting screws.
5. Install — Mount the new transformer and reconnect primary (line) and secondary (24V) leads exactly per your photo.
6. Test — Restore power and verify 24V across the secondary and normal furnace operation.

Signs You Need a Replacement

• Blank thermostat / no low-voltage power
• 0V reading across the transformer secondary
• Furnace completely unresponsive to a heat call
• Burnt smell or discoloration on the transformer body

Shipping & Returns

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