OEM Carrier Transformer 40VA 120V to 24V for Model C4850C50AK05151

This OEM replacement transformer (part number HT01BD236) is the factory-specified step-down control transformer for the Carrier C4850C50AK05151 packaged unit. The transformer converts 120V line voltage to the 24V AC signal that powers your thermostat, control board, and all low-voltage switching circuits. When it fails, the entire control circuit goes dark — the thermostat becomes unresponsive, the system won't call for heating or cooling, and no error codes are generated because the board itself has no power. If you're measuring 120V at the primary and 0V at the secondary, this transformer is your culprit.

• Specs: Input: 120V AC | Output: 24V AC | 40VA rating | OEM part number HT01BD236 | Factory-matched primary and secondary winding tolerances
• OEM vs Generic: OEM transformers are wound to exact VA and voltage tolerances required by the Carrier control board. Undersized or off-tolerance generic units can cause erratic low-voltage behavior, nuisance tripping of the secondary fuse, or premature control board failure.
• Install difficulty: 2/5 — Shut off all power to the unit at the disconnect before servicing. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter. Label and photograph all wire connections before removal. Verify 0V on both primary terminals before handling.
• Warranty: 1-year OEM factory warranty against defects in materials and workmanship. Orders placed before cutoff ship same business day from our warehouse.

Compatibility: Engineered for the Carrier C4850C50AK05151 packaged unit. Verify your existing transformer's input/output voltage and VA rating on the unit's data plate or wiring diagram before ordering — mismatched VA ratings can damage downstream control components. Our team is available to confirm fitment before you purchase.