OEM Carrier Control Transformer 40VA 208/230–24V for Model PY3GNAA42090AA

The Carrier HT01BD209 is the factory OEM control transformer for the PY3GNAA42090AA HVAC system. This transformer steps down 208/230V line voltage to the 24V signal voltage that powers your thermostat, control board, contactor coil, and all other low-voltage control components. When this transformer fails, the entire control circuit goes dark — the thermostat goes blank, nothing responds to a call for heating or cooling, and the system appears completely dead. It is one of the most common and most misdiagnosed failures in residential and light commercial HVAC systems.

• Specs: 208/230V Primary | 24V Secondary | 40VA rated | 50/60 Hz | Class 2 control transformer | OEM Part # HT01BD209
• OEM vs Generic: This is a genuine Carrier OEM transformer wound to exact factory VA and voltage specifications. Generic transformers often run low on secondary voltage under load, causing erratic thermostat behavior, nuisance lockouts, and premature contactor coil failure.
• Install difficulty: 2/5 — Always shut off power at the disconnect and breaker before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter, wire labels or tape. Photograph all wiring connections before disconnecting. Primary wires connect to line voltage terminals; secondary wires feed the 24V control circuit.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed for the Carrier PY3GNAA42090AA. Also replaces legacy Carrier part numbers HT01BD207, HT01CN232, and 9076-00. Verify your unit's control transformer VA rating and primary voltage on the equipment data plate before ordering. Need fitment confirmation? Our HVAC parts specialists verify compatibility before you buy — just reach out before placing your order.