OEM Carrier Transformer 40VA 120V to 24V for Model FK4DNF003000AAAA

This is the factory OEM replacement transformer (part number HT01CN236) for the Carrier FK4DNF003000AAAA fan coil air handler. The transformer steps line voltage (120V) down to the 24V signal voltage required to power the control board, thermostat circuit, and all low-voltage switching components. When the transformer fails, the entire control circuit goes dead — your thermostat will appear blank or unresponsive, and the system will not heat, cool, or run the fan regardless of thermostat input. A failed transformer is often caused by a wiring short in the 24V circuit, so always inspect low-voltage wiring before installing the replacement.

• Specs: 40VA rating | 120V primary / 24V secondary | OEM part number HT01CN236 | Factory-matched output for stable control voltage
• OEM vs Generic: The OEM HT01CN236 transformer is wound to Carrier's exact VA and voltage tolerance specifications. Generic transformers may run marginally low on output voltage, causing erratic thermostat behavior, nuisance lockouts, or premature control board failure.
• Install difficulty: 2/5 — Shut off all power at the breaker before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (to verify 24V output after install). Photograph all wiring connections before disconnecting. Check for shorted low-voltage wiring before energizing.
• Warranty: 1-year OEM factory warranty. Orders placed before cutoff ship same business day from our stocked warehouse.

Compatibility: Designed as the direct factory replacement for Carrier model FK4DNF003000AAAA fan coil air handlers. Verify your existing transformer's VA rating and primary/secondary voltages against your unit's data plate before ordering. Our HVAC parts specialists are available to confirm fitment — just reach out before you order.