OEM Carrier Transformer 40VA 120V–24V for Model C4850C50AW03661

This is the factory-specified OEM replacement transformer (part number HT01BD236) for the Carrier C4850C50AW03661 packaged unit. The transformer steps down 120V line voltage to the 24V signal required by the control board, thermostat, and all low-voltage control circuit components. When this transformer fails, the entire control circuit goes dead — the thermostat becomes unresponsive, the system won't call for heating or cooling, and no diagnostic codes will display. It is often the first component to check when nothing works but the disconnect is confirmed live.

• Specs: 40VA rating | Primary voltage: 120V | Secondary voltage: 24V | OEM part number HT01BD236 | Factory-matched to Carrier C4850C50AW03661 electrical specifications
• OEM vs Generic: This OEM unit is wound to Carrier's exact VA rating and insulation class, ensuring reliable 24V output under full control-circuit load. Undersized generic transformers can sag voltage under load, causing erratic board behavior and nuisance lockouts.
• Install difficulty: 2/5 — Shut off all power at the disconnect before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or terminal connectors. Confirm primary and secondary wiring polarity before energizing. Photograph existing wiring before disconnecting.
• Warranty: 1-year OEM factory warranty. In-stock units ship same business day from our warehouse when ordered before cutoff.

Compatibility: Designed and verified for Carrier model C4850C50AW03661 packaged units. Always confirm your existing transformer's VA rating and voltage markings on the unit data plate before ordering to ensure an exact match. Have questions about fitment? Our HVAC parts specialists verify compatibility before you order — reach out before purchasing.