OEM Carrier 40VA Control Transformer HT01CN236 for Model FK4DNF005000AAAA

This OEM control transformer (part number HT01CN236) is the factory-specified replacement for the Carrier FK4DNF005000AAAA fan coil air handler. The transformer steps down line voltage (120V) to the 24V signal voltage that powers your thermostat, control board, and all low-voltage safety controls. When this component fails, the entire control circuit goes dead — the thermostat goes blank, the system will not respond to any calls for heating or cooling, and no fault codes are generated because the board itself has no power.

• Specs: 40VA rating | 120V primary / 24V secondary | Factory-matched OEM part number HT01CN236 | Drop-in replacement with original mounting footprint
• OEM vs Generic: OEM transformers are wound and insulated to Carrier's exact VA and thermal specifications. Generic alternatives often run hot under continuous load and are more prone to early failure from voltage spikes — a common cause of repeated transformer burnout.
• Install difficulty: 2/5 — Shut off all power to the air handler before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter. Verify 120V input and 24V output after installation before restoring full power. Photograph all wiring connections before disconnecting the old unit.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our HVAC parts warehouse.

Compatibility: Designed specifically for the Carrier FK4DNF005000AAAA fan coil air handler. Always verify your unit's data plate voltage ratings and VA requirement before ordering. If you are experiencing repeated transformer failures, inspect the 24V secondary circuit for shorts before installing the replacement. Our parts specialists are available to confirm fitment — reach out before you order.