OEM Carrier Control Transformer 40VA 208/240V to 24V for Model PY3GNA030040AB

This OEM Carrier control transformer (part #HT01BD209) is the factory-specified replacement for the Carrier PY3GNA030040AB packaged unit. The transformer steps down high-voltage line power (208/240V) to the 24V DC signal required by the control circuit — powering the thermostat, contactor coil, and every low-voltage control component in the system. When it fails, the entire control circuit goes dark: the thermostat becomes unresponsive, the unit will not start, and no fault codes will display on the board. A failed transformer is often misdiagnosed as a control board failure, making correct identification critical before ordering replacement parts.

• Specs: 208/240V primary input | 24V secondary output | 40VA power rating | 50/60Hz | Factory-matched OEM tolerances for the Carrier PY3GNA030040AB
• OEM vs Generic: OEM transformers are wound to exact VA and voltage tolerances. Undersized or off-spec generic units can cause erratic thermostat behavior, nuisance tripping of the low-voltage fuse, or premature contactor coil failure.
• Install difficulty: 2/5 — Always shut off all power to the unit at the disconnect before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter (to verify 24V output after installation), wire nuts or spade connectors. Photograph all wiring before disconnecting terminals. Test for 24V output and check the low-voltage fuse before condemning the transformer.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed as a direct OEM replacement for Carrier model PY3GNA030040AB. Verify primary voltage on your unit's data plate (208V or 240V configurations) before ordering. Not sure this is the right part? Our HVAC parts specialists verify fitment before you order — contact us today and get your system back online fast.