OEM Carrier Transformer 40VA 120V/24V for Model FB4CNF042T00ABAA

This is the OEM replacement transformer (part number HT01CN241) for the Carrier FB4CNF042T00ABAA fan coil air handler. The transformer steps down 120V line voltage to the 24V AC signal that powers your entire control circuit — including the thermostat, contactor coil, and control board. When this transformer fails, the system goes completely silent: the thermostat goes blank, no call for heat or cooling is answered, and nothing responds. If your system has power at the disconnect but zero 24V output at the transformer's secondary terminals, this part is the likely culprit.

• Specs: 40VA rating | Primary: 120V AC | Secondary: 24V AC | OEM part number HT01CN241 | Factory-matched output tolerance for stable control circuit operation
• OEM vs Generic: OEM transformers from Carrier are wound to exact VA and voltage specifications. Off-brand substitutes often deliver slightly off 24V output, which can cause erratic thermostat behavior, chattering contactors, and premature control board failure — costing far more than the price difference.
• Install difficulty: 2/5 — Shut off power at the disconnect and breaker before starting. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or quick-connect terminals. Always verify 0V at primary terminals with a meter before handling. Label all low-voltage wiring before disconnecting.
• Warranty: 1-year OEM factory warranty. In-stock units ship same business day from our warehouse.

Compatibility: Designed specifically for the Carrier FB4CNF042T00ABAA fan coil air handler. Verify your existing transformer's VA rating and primary/secondary voltages on the data plate or wiring diagram inside the unit before ordering. Our fitment team is available to confirm compatibility before you purchase — orders placed before 3PM EST ship the same business day.