OEM Carrier Control Transformer 40VA 120V/24V for Model C48A502751

This is the factory-specified OEM replacement transformer (part number HT01BD236) for the Carrier C48A502751 packaged unit. The transformer steps down line voltage (120V) to the 24V signal that powers your thermostat, control board, contactor coil, and every other low-voltage component in the system. When this part fails, the entire control circuit goes dead — the thermostat goes blank, the system won't respond to any call for heating or cooling, and nothing turns on. It is one of the first components to check during a no-power diagnostic.

• Specs: Input 120VAC | Output 24VAC | 40VA rated | OEM part number HT01BD236 | Factory-matched windings and mounting configuration for direct drop-in replacement
• OEM vs Generic: The OEM transformer is wound to exact VA and voltage tolerances required by the Carrier C48A502751 control board. Undersized or off-tolerance generic transformers can overheat, trip internal thermal fuses, and damage downstream control components — costing far more than the part itself.
• Install difficulty: 2/5 — Shut off all power at the disconnect before beginning. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter, and wire nuts or spade terminals. Label or photograph all wiring connections before removal. The transformer mounts to the control panel with a single bracket screw in most configurations.
• Warranty: 1-year OEM factory warranty against defects. In stock and ships same business day from our warehouse.

Compatibility: Designed specifically for the Carrier C48A502751 packaged unit. Always verify your existing transformer's input/output voltage and VA rating against your unit's data plate before ordering. If your thermostat is completely unresponsive and breakers are confirmed good, this transformer is your most likely culprit. Order today and our team will confirm fitment before your order ships.