Tempstar 40VA Transformer for T8MPN075B12B2 — 115V to 24V | Ships Today

Overview

This OEM 40VA control transformer (part 1172810) supplies the low-voltage power for the Tempstar T8MPN075B12B2 furnace. It steps incoming 115V line voltage down to the 24V required by the control board, thermostat, gas valve, and relays. A failed transformer is a classic cause of a completely dead furnace — no thermostat display, no blower, no ignition. This direct-fit replacement restores the 24V control circuit so the system can power up and sequence normally.

Specifications

Compatibility

Built for the Tempstar T8MPN075B12B2 and shared ICP/Heil/Comfortmaker furnaces using the 40VA 115-to-24V transformer (1172810). Verify primary voltage and VA rating against your existing transformer before installing.

Installation Guide

1. Safety First — Disconnect power and verify zero voltage at the transformer with a multimeter.
2. Access — Remove the furnace control/service panel.
3. Document — Photograph the primary and secondary wire connections before disconnecting.
4. Remove — Label and disconnect the leads, then unbolt the old transformer from the panel.
5. Install — Mount the new transformer and reconnect the 115V primary and 24V secondary leads exactly per your photo.
6. Test — Restore power and confirm 24V across the secondary, then run a full heat cycle.

Signs You Need a Replacement

• Furnace is completely dead — no thermostat power or response
• No measurable 24V across the transformer secondary
• Transformer is hot, buzzing, or shows scorched/melted housing
• Repeated blown control fuse traced to a shorted transformer

Shipping & Returns

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