OEM Carrier 40VA Control Transformer (HT01BD236) for Model C4850C48AY03561

This is the factory OEM replacement transformer for the Carrier C4850C48AY03561 packaged unit. The control transformer steps line voltage (120V) down to the 24V signal voltage that powers your thermostat, control board, contactor coil, and all low-voltage safety circuits. When this transformer fails, the entire control circuit goes dead — your thermostat goes blank, the system stops responding to calls for heating or cooling, and no components will energize. If you're reading 0V at your 24V secondary terminals, this transformer is the first place to check.

• Specs: OEM Part Number HT01BD236 | 40VA rating | Primary: 120V | Secondary: 24V | Hardwired terminal connections | Factory-matched impedance and thermal protection
• OEM vs Generic: OEM transformers from Carrier use UL-listed cores wound to exact VA and voltage specifications. Undersized or off-tolerance generic transformers can overload under heavy relay switching, causing nuisance trips or premature failure of downstream control boards.
• Install difficulty: 2/5 — Disconnect all power before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or spade connectors. Always verify 0V at primary terminals before handling. Label all low-voltage wiring prior to disconnecting the old unit.
• Warranty: 1-year OEM factory warranty. Ships same business day from our stocked warehouse.

Compatibility: Engineered as the direct OEM replacement for Carrier model C4850C48AY03561 packaged units. Confirm your existing transformer's VA rating and primary/secondary voltages on the unit data plate or wiring diagram before ordering. Our parts specialists are available to verify fitment — order with confidence and get back up and running fast. In stock — ships today.