OEM Carrier Transformer 40VA 120V/24V for Model M150039MX41011525

This OEM replacement transformer (part number HT01BD118) is the factory-specified control circuit transformer for the Carrier M150039MX41011525. The transformer steps down line voltage (120V) to the 24V signal voltage required to power the control board, thermostat, and all low-voltage switching circuits. When this component fails, the entire control circuit goes dark — you'll see a blank thermostat, no response from the system, or a tripped low-voltage fuse that immediately blows again upon replacement.

• Specs: Primary: 120V AC | Secondary: 24V AC | VA Rating: 40VA | OEM Part Number: HT01BD118 | Factory-matched windings and thermal protection
• OEM vs Generic: OEM transformers from Carrier are wound to exact VA and voltage tolerances, ensuring stable 24V output under full control-circuit load. Generic alternatives often exhibit voltage sag under load, which can cause erratic board behavior, false fault codes, and premature contactor coil failure.
• Install Difficulty: 2/5 — Disconnect power at the breaker and confirm zero voltage with a multimeter before beginning. Tools needed: flathead and Phillips screwdrivers, wire nuts or spade connectors, multimeter. Label all wiring before disconnecting. Verify 24V output at secondary terminals after installation before restoring full system power.
• Warranty: 1-year OEM factory warranty against defects in materials and workmanship. Orders placed before cutoff ship same business day from our stocked warehouse.

Compatibility: Designed for the Carrier M150039MX41011525. Always confirm your unit's control circuit voltage and VA requirements on the equipment data plate before ordering. If your thermostat is unresponsive or your low-voltage fuse keeps blowing, this transformer is the most likely root cause. Our fitment team is available to verify compatibility before you order — don't guess on a control circuit component.