OEM Carrier Control Transformer 40VA 208/230V to 24V for Model PY3GNA030040AA

This OEM control transformer (part number HT01BD209) is the factory-specified replacement for the Carrier PY3GNA030040AA HVAC system. The transformer steps down high-voltage line power (208/230V) to the 24V signal voltage that runs your thermostat, control board, relays, and all low-voltage components. When this transformer fails, the entire control circuit goes dark — you'll see a blank thermostat, no response to calls for heating or cooling, and no board activity whatsoever. It is one of the most commonly overlooked failure points in a complete system no-start diagnosis.

• Specs: 40VA rated | 208/230V primary input | 24V secondary output | 50/60 Hz | Class 2 control transformer | Approx. 1 lb.
• OEM vs Generic: This is a genuine Carrier OEM part, wound to exact factory VA and voltage tolerances. Undersized or off-spec aftermarket transformers can sag under full control-circuit load, causing intermittent lockouts and premature board failures.
• Install difficulty: 2/5 — Shut off all power at the disconnect and breaker before touching any wiring. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter (verify 24V output after install). Label all wires before disconnecting. This is a straightforward swap for any experienced DIYer or technician.
• Warranty: 1-year OEM factory warranty. Ships same business day from our warehouse.

Compatibility: Designed as a direct OEM replacement for Carrier model PY3GNA030040AA. This part also replaces prior Carrier transformer part numbers HT01BD207, HT01CN232, and 9076-00 — verify your unit's data plate and existing wiring configuration before ordering. Have a fitment question? Our HVAC parts specialists confirm compatibility before your order ships.