OEM Carrier Transformer 40VA 120V to 24V for Model FX4DNF037000AAAA

This is the factory OEM replacement transformer (part number HT01CN241) for the Carrier FX4DNF037000AAAA fan coil air handler. The transformer steps down 120V line voltage to the 24V AC signal that powers your thermostat, control board, contactor coil, and every other low-voltage component in the system. When this part fails, the entire control circuit goes dead — the thermostat goes blank, the system will not respond to any call for heating or cooling, and no diagnostic codes will appear because the board itself has no power. It is one of the most overlooked yet most critical components in any HVAC system.

• Specs: 40VA rated | 120V primary / 24V secondary | Ring-style mounting | OEM part number HT01CN241 | Factory-matched output tolerance for stable low-voltage control
• OEM vs Generic: OEM transformers are wound and potted to Carrier's exact VA and voltage specifications. Undersized or off-tolerance generic transformers can trip on thermal overload, cause erratic board behavior, or fail prematurely under full control-circuit load.
• Install difficulty: 2/5 — Disconnect power at the breaker and verify zero voltage with a multimeter before touching any wiring. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or spade connectors. Photograph all wiring connections before removal.
• Warranty: 1-year OEM factory warranty against defects. In-stock units ship same business day from our warehouse when ordered before 3PM local time.

Compatibility: Designed specifically for the Carrier FX4DNF037000AAAA fan coil air handler. Always verify your unit's data plate shows 120V primary input before ordering. If your existing transformer is tripping repeatedly, inspect for a short in the 24V wiring harness before installing the replacement — a shorted secondary will damage the new unit immediately. Our fitment team is available to confirm compatibility before you order.