Tempstar 40VA Transformer for T9MPD075F12C1 — 115V to 24V Step-Down | Ships Today

Overview

This genuine OEM control transformer, part #1172810, supplies low-voltage power to the Tempstar T9MPD075F12C1 gas furnace. It steps 115V line voltage down to 24V at 40VA, powering the control board, thermostat circuit, gas valve, and relays. When a transformer fails — usually from a shorted secondary, an overloaded 24V circuit, or simple age — the furnace goes completely dead at the thermostat: no display, no blower, no ignition. A blown low-voltage fuse on the control board that pops repeatedly is also a classic sign of a failing transformer or a short downstream of it. This 40VA OEM unit matches the original mounting, primary/secondary voltages, and VA rating for a direct replacement.

Specifications

Compatibility

Built for the Tempstar T9MPD075F12C1 gas furnace and other ICP-family units (Heil, Comfortmaker, Day & Night) that use a 115V-to-24V 40VA transformer. Verify primary/secondary voltage and VA rating against your original.

Installation Guide

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

Signs You Need a Replacement

• Furnace completely dead — no thermostat or control display
• Repeatedly blown 24V control-board fuse
• No measurable 24V output at the secondary terminals
• 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.