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This OEM replacement transformer (part number HT01CN241) is the factory-specified control circuit transformer for the Carrier FY5BNF042000AAAA fan coil unit. Its job is to step down 120V line voltage to the 24V AC signal that powers your thermostat, control board, and all low-voltage components. When it fails, the entire control circuit goes dark — the thermostat becomes unresponsive, the system will not call for heating or cooling, and no safety or diagnostic functions operate. A failed transformer is often misdiagnosed as a bad control board, so always check transformer output with a multimeter before replacing more expensive components.
Compatibility: Designed for the Carrier FY5BNF042000AAAA fan coil unit. Cross-reference OEM part number HT01CN241 against your unit's wiring diagram and data plate to confirm primary voltage and VA rating before ordering. Our parts specialists are available to verify fitment — order with confidence and get back to comfort faster.