OEM Carrier Control Transformer 40VA 120V–24V for Model PY4GPAA36090AA

This OEM control transformer (part number HT01BD209) is the factory-specified replacement for the Carrier PY4GPAA36090AA packaged unit. The transformer steps down line voltage (120V primary) to the 24V AC signal used by the low-voltage control circuit — powering the thermostat, contactor coils, gas valve, and all safety controls. When the transformer fails, the entire control circuit goes dark: the thermostat shows no power, nothing responds to a call for heating or cooling, and the system appears completely dead.

• Specs: 40VA rating | 120V primary / 24V secondary | OEM part number HT01BD209 | Factory-matched winding and mounting dimensions
• OEM vs Generic: This is the exact factory OEM transformer. OEM units are wound to precise VA tolerances, ensuring reliable coil pull-in and preventing nuisance tripping of the built-in secondary fuse. Generic transformers can run under-rated, causing overheating and premature failure.
• Install difficulty: 2/5 — Always disconnect power at the disconnect box before servicing. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (verify 24V output after install). Label all low-voltage wires before disconnecting.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Engineered for the Carrier PY4GPAA36090AA packaged unit. Always verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate before ordering. Our HVAC parts specialists are available to confirm fitment — contact us before you order if you have any questions.