OEM Carrier Control Transformer 40VA 120V/24V for Model PY3PNA042090NB

This is the genuine OEM replacement transformer for the Carrier PY3PNA042090NB packaged unit. The transformer is the heartbeat of your system's low-voltage control circuit — it steps down 120V line voltage to the 24V signal voltage required by your thermostat, contactor coil, gas valve, and control board. When it fails, nothing works: no call for heat or cool reaches any component, and the system goes completely unresponsive. A blown fuse on the secondary winding or a shorted coil are the most common failure modes.

• Specs: 40VA rated | Primary: 120V AC | Secondary: 24V AC | OEM Part Number: HT01BD209 | Factory-matched for Carrier PY3PNA042090NB packaged units
• OEM vs Generic: OEM transformers are wound and insulated to Carrier's exact VA and voltage tolerance specs. Undersized or off-tolerance generic units can fail under high-demand conditions, repeatedly blowing the 3A control fuse and masking the root cause of the problem.
• Install Difficulty: 2/5 — Shut off all power at the disconnect before beginning. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter. Always test secondary voltage output (should read 24–28V AC) after installation before restoring thermostat wiring. Photograph all wiring before disconnecting.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed for the Carrier PY3PNA042090NB packaged unit (4-ton, 90,000 BTU gas/electric combination). Verify your existing transformer's VA rating and primary/secondary voltages on the unit's data plate before ordering. Our technical team is available to confirm fitment — contact us before you order if you have any questions.