Tempstar 40VA Transformer for T8DNL075B12B1 – 115V to 24V Furnace Control | Ships Today

Overview

This is a genuine OEM control transformer (part number 1172810) for the Tempstar T8DNL075B12B1 gas furnace. It steps down incoming 115-volt line power to the 24-volt control voltage that powers your thermostat, gas valve, igniter circuit, and control board. Rated at 40VA, it delivers enough current to run every low-voltage component on the furnace at once. When a transformer fails, the entire 24V control circuit goes dead: the thermostat may go blank, the furnace ignores a call for heat, and you may notice a burnt smell or scorched windings. A buzzing or hot-running transformer is also a sign of imminent failure.

Specifications

Compatibility

Engineered as a direct-fit replacement for the Tempstar T8DNL075B12B1 furnace. The same 1172810 transformer is shared across many ICP-family gas furnaces (Tempstar, Heil, Comfortmaker, Arcoaire) using a 115V primary / 24V secondary 40VA control circuit. Confirm your existing transformer is rated 115/24V 40VA before ordering.

Installation Guide

1. Safety First – Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter at the transformer leads.
2. Access – Remove the furnace control/blower compartment service panel.
3. Document – Photograph all primary and secondary wire connections before disconnecting anything.
4. Remove – Disconnect the line-voltage primary leads and the 24V secondary leads, then unbolt the transformer from its mounting bracket.
5. Install – Mount the new transformer, reconnect primary and secondary leads exactly per your photo, and secure all connections.
6. Test – Restore power and confirm 24V across the secondary, then run a heat cycle to verify normal operation.

Signs You Need a Replacement

• Furnace completely unresponsive to a call for heat with a dead thermostat
• No 24V reading across the secondary leads
• Visible scorching, melted windings, or a burnt smell at the transformer
• Audible buzzing or the transformer running excessively hot

Shipping & Returns

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