OEM Carrier Transformer 40VA 120V to 24V for Model M150039MX41011524

This OEM replacement transformer (part number HT01BD118) is the factory-specified control circuit transformer for the Carrier M150039MX41011524. Its job is to step down line voltage from 120V to the 24V AC signal that powers your thermostat, control board, and all low-voltage safety circuits. When this transformer fails, the entire control circuit loses power — your thermostat goes blank, the system won't respond to calls for heating or cooling, and nothing works. A faulty transformer is often misdiagnosed as a failed control board, so always verify 24V output at the transformer secondary before replacing more expensive components.

• Specs: Primary voltage: 120V AC | Secondary voltage: 24V AC | VA rating: 40VA | OEM part number: HT01BD118 | Factory-matched output tolerance
• OEM vs Generic: This OEM unit is wound and rated to Carrier's exact factory specifications. Generic transformers often use lower-grade core laminations that run hotter, reducing lifespan and risking nuisance tripping of the internal thermal fuse under normal load conditions.
• Install difficulty: 2/5 — Shut off all power to the unit before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (to verify 24V output after install). Photograph or label all low-voltage wire connections before disconnecting. Reconnect wires to matching terminals and restore power to confirm 24V output.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed as a direct OEM replacement for Carrier model M150039MX41011524. Verify your existing transformer's primary/secondary voltages and VA rating on the data plate before ordering to ensure a proper match. Have a question about fitment? Our HVAC parts specialists confirm compatibility before you order — reach out before placing your order.