OEM Carrier Transformer 40VA 120V–24V for Model PY3GNA042090AB

This OEM step-down transformer (part number HT01BD209) is the factory-specified replacement for the Carrier PY3GNA042090AB packaged unit. The transformer converts 120V line voltage to the 24V AC signal that powers the control board, thermostat circuit, and all low-voltage switching in the system. When this component fails, the entire control circuit goes dead — no thermostat response, no contactor pull-in, and no ignition sequence will occur, making it one of the first components to check when diagnosing a completely unresponsive unit.

• Specs: 40VA rated | 120V primary / 24V secondary | Class 2 transformer | Factory-matched output tolerance for stable control-circuit voltage
• OEM vs Generic: The OEM HT01BD209 is wound and potted to Carrier's exact VA and voltage specifications. Generic transformers may output slightly off-voltage 24V, which can cause nuisance lockouts, erratic board behavior, or premature control board failure over time.
• Install difficulty: 2/5 — Shut off all power at the disconnect and breaker before replacing. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (to verify 24V output after install). Photograph all low-voltage wire connections before disconnecting.
• Warranty: 1-year OEM factory warranty against defects. Orders ship same business day from our warehouse when placed before 3 PM local time.

Compatibility: Designed as a direct OEM replacement for Carrier model PY3GNA042090AB. Always verify the VA rating and primary/secondary voltages against your unit's data plate and existing transformer label before ordering. Our HVAC parts specialists are available to confirm fitment — contact us before you order if you have any questions.