OEM Carrier 40VA Control Transformer HT01BD702 for Model C50A403564

This is the factory OEM replacement transformer for the Carrier C50A403564 commercial packaged unit. The transformer steps down 120V line voltage to the 24V signal required by your thermostat, control board, contactor coil, and every other low-voltage component in the system. When this part fails, absolutely nothing works — the thermostat goes dark, the contactor won't pull in, and the unit sits completely unresponsive. A failed transformer is often the first thing to check when a system appears totally dead with no fault codes.

• Specs: OEM Part Number HT01BD702 | 40VA rated | Primary: 120V | Secondary: 24V | Factory-matched to Carrier C50A403564 control circuit requirements
• OEM vs Generic: This OEM transformer is wound to exact factory VA and voltage tolerances. Undersized or off-tolerance generic transformers can overheat, blow the 3A control fuse repeatedly, or deliver insufficient voltage to fire the gas valve or energize the contactor — causing intermittent callbacks and misdiagnosis.
• Install difficulty: 2/5 — Shut off all power before servicing. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter. Verify 0V at transformer primary before disconnecting leads. Label all wires before removal and confirm secondary output reads 24–28V AC after install.
• Warranty: 1-year OEM factory warranty against defects. In stock — ships same business day from our HVAC-dedicated warehouse.

Compatibility: Designed specifically for Carrier C50A403564 commercial rooftop/packaged units using OEM part number HT01BD702. Always verify your existing transformer's VA rating and primary/secondary voltages against your unit's wiring diagram before ordering. Our fitment team is available to confirm compatibility before you buy — no guesswork required.