OEM Carrier 40VA Control Transformer HT01BD236 for Model C4850C50AY03051

This is the factory OEM replacement control transformer (part# HT01BD236) for the Carrier C4850C50AY03051 packaged unit. The transformer steps down 120V primary voltage to 24V AC, powering the entire low-voltage control circuit — including the thermostat, contactor coil, gas valve, and control board. When this component fails, the system goes completely unresponsive: the thermostat goes blank, no heating or cooling stages engage, and the unit will not respond to any call for conditioning. A failed transformer is one of the most common causes of a completely dead HVAC system.

• Specs: 40VA rating | 120V primary / 24V secondary | OEM part number HT01BD236 | Factory-matched windings and core for full compatibility with Carrier C4850C50AY03051 control circuitry
• OEM vs Generic: OEM transformers are wound to exact VA and voltage tolerances, protecting sensitive control boards from under- or over-voltage. Generic units often lack proper overcurrent protection, risking board damage on a fault condition.
• Install Difficulty: 2/5 — Disconnect all power before beginning. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter. Verify 24V output after installation before closing the panel. Always check for a shorted control wire that may have caused the original transformer failure — replacing the transformer without clearing the short will blow the new unit immediately.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed specifically for the Carrier C4850C50AY03051 packaged unit. Confirm your existing transformer's VA rating and primary/secondary voltages on the data plate before ordering. If you're unsure of fitment, our HVAC parts team will verify compatibility before your order ships — same-day shipping on all in-stock OEM parts.