OEM Carrier Transformer 40VA 120V–24V for Model FV4CNF003000AAAA

This OEM replacement transformer (part number HT01CN236) is the factory-specified control circuit transformer for the Carrier FV4CNF003000AAAA fan coil air handler. Its job is to step down line voltage from 120V to the 24V signal required by the thermostat, control board, and all low-voltage accessories. When this transformer fails, the entire control circuit goes dark — your thermostat shows no power, the system won't respond to calls for heating or cooling, and nothing works despite line voltage being present at the unit. A failed transformer is one of the most commonly misdiagnosed HVAC faults, often mistaken for a bad control board or thermostat.

• Specs: 40VA rating | Primary: 120V | Secondary: 24V | OEM part number HT01CN236 | Factory-matched for Carrier FV4CNF003000AAAA air handler
• OEM vs Generic: This is a genuine OEM Carrier transformer manufactured to exact VA, voltage, and physical mounting specifications. Generic transformers frequently run at reduced VA capacity, causing overheating and premature failure — especially when multiple 24V accessories are wired to the circuit.
• Install difficulty: 2/5 — Always shut off power at the disconnect and breaker before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or terminal connectors. Verify output voltage (should read 24–28V AC) after installation before reassembling the panel.
• Warranty: 1-year OEM factory warranty against defects. In-stock and ships same business day from our warehouse.

Compatibility: Designed specifically for the Carrier FV4CNF003000AAAA fan coil air handler. Always verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate before ordering. If you have any questions about fitment, our HVAC parts specialists confirm compatibility before you buy — no guesswork required.