OEM Carrier 40VA Control Transformer HT01CN236 for Model FK4DNB003000AAAA

This OEM replacement transformer (part number HT01CN236) is the factory-specified control transformer for the Carrier FK4DNB003000AAAA air handler. The transformer steps down 120V line voltage to the 24V signal voltage required by the control board, thermostat, and all low-voltage control circuit components. When this transformer fails, the entire control circuit goes dead — your thermostat shows no response, the system won't heat or cool, and no safety or staging functions operate. It is often the first component to diagnose when nothing responds at all.

• Specs: 40VA rating | 120V primary / 24V secondary | OEM part number HT01CN236 | Factory-matched output voltage and VA capacity for Carrier FK4DNB003000AAAA air handler control circuits
• OEM vs Generic: OEM transformers are wound and insulated to exact factory VA and voltage tolerances. Undersized or off-spec generic units can overheat under sustained low-voltage load, tripping the internal fuse and leaving you in the same no-heat, no-cool situation within a season.
• Install difficulty: 2/5 — Disconnect all power to the unit before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (to confirm 24V output after install). Always photograph wiring connections before removing the old transformer.
• Warranty: 1-year OEM factory warranty included. Orders placed by 3 PM local time ship same business day from our climate-controlled parts warehouse.

Compatibility: Designed and factory-matched for the Carrier FK4DNB003000AAAA air handler. Verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate before ordering. Our parts specialists are available to confirm fitment — reach out before you buy if you have any questions.