ICP Transformer for WFML090B042B2 — 40VA 120/24V | Ships Today

Overview

This is a genuine OEM 40VA control transformer (part #1177217) for the ICP Tempstar Heil WFML090B042B2 gas furnace. The transformer steps the incoming 120V line voltage down to the 24V low-voltage power that runs the control board, thermostat, gas valve, igniter circuit, and blower relays. Rated at 40VA, it delivers enough current to energize all the furnace's low-voltage loads at once. When a control transformer fails, the entire 24V control circuit goes dead — the thermostat screen goes blank, the furnace ignores any call for heat, and no relays pull in. A buzzing or overheated transformer, or a low-voltage fuse that keeps blowing, signals the transformer is shorting or failing under load.

Specifications

Compatibility

Engineered as a direct OEM replacement for the ICP Tempstar Heil WFML090B042B2 furnace. The same 40VA 120/24V transformer is used across many ICP-family gas furnaces sold under the Tempstar, Heil, Comfortmaker, and Arcoaire brands. Always confirm your existing transformer is a 120V primary / 24V secondary, 40VA unit before ordering.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage at the transformer terminals with a multimeter.
2. Access — Remove the furnace blower-compartment service panel to expose the control area.
3. Document — Photograph all primary (line) and secondary (24V) wire connections before disconnecting anything.
4. Remove — Disconnect the line-voltage and 24V leads, then unscrew the transformer from its mounting bracket or panel.
5. Install — Mount the new transformer, reconnect the 120V primary and 24V secondary leads exactly per your photo.
6. Test — Restore power, confirm 24V across the secondary terminals, and verify the thermostat and furnace respond to a call for heat.

Signs You Need a Replacement

• Furnace completely unresponsive — blank thermostat, no 24V control power.
• Repeatedly blown low-voltage fuse on the control board.
• Audible buzzing or a burnt smell from the transformer.
• Measured 24V output is low, missing, or fluctuating under load.

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.