Tempstar 40VA Transformer for TCK125N20B1 — 115V to 24V | Ships Today

Overview

The genuine OEM 40VA control transformer (part #1011626, TRANS 115>24 40VA) for the Tempstar TCK125N20B1 gas furnace. This step-down transformer converts 115V line voltage to the 24V control voltage that powers the thermostat, control board, gas valve, and relays. A failed transformer leaves the entire low-voltage control circuit dead — no thermostat display, no call for heat or cool, and no 24V at the board. Transformers commonly fail from a shorted gas valve, a pinched thermostat wire, or a control board fault overloading the secondary.

Specifications

Compatibility

Designed for the Tempstar TCK125N20B1 and shared across many ICP-family furnaces and air handlers (Tempstar, Heil, Comfortmaker, Arcoaire) that use a 40VA 115V-to-24V control transformer. Confirm your primary voltage and VA rating 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 control-compartment service panel.
3. Document — Photograph all primary and secondary leads and their terminals before disconnecting.
4. Remove — Disconnect the line and low-voltage leads, unbolt the transformer from the bracket, and remove it.
5. Install — Mount the new transformer, reconnect the 115V primary and 24V secondary leads exactly per your photo, and secure all connections.
6. Test — Restore power and confirm 24V across the secondary and a normal thermostat response.

Signs You Need a Replacement

• Blank thermostat / no 24V control power
• Furnace completely unresponsive to a call for heat
• No measurable voltage across the transformer secondary
• Burnt smell or visibly scorched transformer windings

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.