ICP 40VA Transformer for WFSR100C042A1 — 120/24V | Ships Today

Overview

This genuine OEM control transformer (part number 1177217) supplies low-voltage power for the ICP/Tempstar/Heil WFSR100C042A1 furnace. It steps the 120V line voltage down to the 24V needed by the control board, thermostat, gas valve, and ignition circuit. Rated at 40VA, it provides ample current for standard furnace controls. When a transformer fails — usually from a shorted thermostat wire, a failed gas valve coil, or simple age — the entire 24V control system goes dead: no thermostat display, no call for heat, and no blower or ignition response. Replacing the transformer with a correct 40VA, 120-to-24V unit restores full control power.

Specifications

Compatibility

Factory transformer for the ICP/Tempstar/Heil WFSR100C042A1 and a wide range of ICP-family gas furnaces using 120V primary control power. Verify your existing primary voltage is 120V (not 208/240V) before installing.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter.
2. Access — Remove the control-compartment service panel.
3. Document — Photograph all primary and secondary wire connections before disconnecting.
4. Remove — Disconnect the leads, remove the mounting screws, and take out the failed transformer.
5. Install — Mount the new transformer, reconnect 120V to the primary and 24V to the secondary exactly per your photo.
6. Test — Restore power and confirm 24V at the secondary and a normal thermostat call for heat.

Signs You Need a Replacement

• Thermostat is blank or unresponsive
• No 24V reading at the control board with line power present
• Furnace will not respond to a call for heat
• Burnt smell or visible scorching on the transformer windings

Shipping & Returns

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