Tempstar 40VA Transformer for T9MPD075F12C2 — 115V to 24V | Ships Today

Overview

This OEM control transformer (part number 1172810) provides the 24V low-voltage power for the Tempstar T9MPD075F12C2 gas furnace. It steps 115V line voltage down to 24V at 40VA, feeding the control board, thermostat circuit, gas valve, and relays. A failed transformer commonly results in a completely dead furnace — no board lights, no blower, and no thermostat response. Typical causes are a shorted thermostat wire, a stuck relay or contactor drawing excess current, or normal winding fatigue with age.

Specifications

Compatibility

Direct OEM replacement for the Tempstar T9MPD075F12C2 furnace and other ICP-family (Tempstar, Heil, Comfortmaker, Arcoaire) units using a 40VA 115-to-24V control transformer. Verify the part number and terminal layout against your existing transformer before installing.

Installation Guide

1. Safety First — Disconnect power at the switch and breaker; verify zero voltage with a multimeter.
2. Access — Remove the furnace front service panel.
3. Document — Photograph every primary and secondary wire connection before disconnecting.
4. Remove — Label and disconnect the wires, then remove the transformer mounting screws.
5. Install — Mount the new transformer and reconnect each wire to its matching terminal per your photo.
6. Test — Restore power, confirm 24V on the secondary, and run a full heat cycle.

Signs You Need a Replacement

• Furnace is completely dead — no control board lights and no thermostat response.
• No 24V measured across the transformer secondary terminals.
• Low-voltage fuse on the control board repeatedly blows.
• Burnt smell or visible scorching 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.