Tempstar Transformer for T8DNL100F14B1 — 115V to 24V 40VA | Ships Today

Overview

This is a genuine OEM control transformer (part number 1172810) for the Tempstar T8DNL100F14B1 gas furnace. The transformer steps down 115-volt line power to the 24-volt low-voltage control circuit that runs your thermostat, gas valve, igniter, and control board. It is rated at 40VA, giving it the capacity to drive the full complement of low-voltage components on a single-stage furnace. When a 24V transformer fails, the entire control system goes dead — the thermostat screen may go blank, the furnace will not respond to a call for heat, and you will often find a blown low-voltage fuse on the control board. A buzzing or humming transformer, a burnt smell near the control compartment, or zero volts at the secondary terminals are all signs the transformer has shorted internally and needs replacement.

Specifications

Compatibility

Designed as the factory transformer for the Tempstar T8DNL100F14B1 furnace. Because Tempstar, ICP, Heil, Comfortmaker, and Arcoaire furnaces share the same parts platform, this 115V-to-24V 40VA transformer also services many comparable single-stage models in that family. Always confirm the printed primary/secondary voltage and VA rating against your old transformer before installing.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter before touching any wiring.
2. Access — Remove the furnace control/blower service panel to expose the control compartment.
3. Document — Photograph every wire on the transformer's primary and secondary terminals before disconnecting anything.
4. Remove — Disconnect the primary (line) and secondary (24V) leads, then unbolt the transformer from its mounting bracket.
5. Install — Mount the new transformer, then reconnect the primary and secondary leads exactly as shown in your photo.
6. Test — Restore power and confirm 24V across the secondary terminals and a normal call for heat.

Signs You Need a Replacement

• Thermostat is blank or unresponsive and the furnace will not start.
• Repeated blown low-voltage fuses on the control board.
• Audible buzzing or humming from the transformer.
• No 24V reading across the secondary terminals.

Shipping & Returns

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