OEM Carrier Transformer 40VA 120V–24V for Model FV4BNF005000AAAA

This is the factory OEM replacement transformer (part number HT01CN236) for the Carrier FV4BNF005000AAAA fan coil air handler. The transformer steps line voltage (120V) down to the 24V AC signal required to power the control board, thermostat circuit, and all low-voltage control components. When this transformer fails, the entire control circuit goes dead — your thermostat will appear unresponsive, the system will not call for heating or cooling, and nothing will happen at startup. A failed transformer is often mistaken for a bad control board, making it the first component to test when your system goes completely unresponsive.

• Specs: 40VA rating | Primary: 120V AC | Secondary: 24V AC | OEM part number HT01CN236 | Factory-matched output tolerance for reliable low-voltage operation
• OEM vs Generic: This OEM transformer is wound and rated to Carrier's exact factory specifications. Generic transformers may deliver inconsistent 24V output, causing nuisance lockouts, erratic thermostat behavior, or premature control board failure due to voltage fluctuation.
• Install difficulty: 2/5 — Disconnect all power before starting. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or push-in connectors. Verify 0V at the primary leads with your multimeter before handling. Photograph all wiring connections before disconnecting the old unit.
• Warranty: 1-year OEM factory warranty against defects. Orders placed before cutoff ship the same business day from our climate-controlled parts warehouse.

Compatibility: Designed specifically for the Carrier FV4BNF005000AAAA fan coil air handler. Confirm your existing transformer's VA rating and primary/secondary voltages on the unit data plate before ordering. If you're unsure of fitment, our HVAC parts specialists are available to verify compatibility before you purchase — no guesswork required.