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This OEM replacement transformer (part number HT01CN241) is the factory-specified step-down transformer for the Carrier FY4ANF018008AAAA fan coil unit. The transformer converts 120V line voltage down to the 24V AC signal that powers the entire control circuit — including the thermostat, control board, and all low-voltage relays. When the transformer fails, the entire system goes silent: the thermostat goes blank, no calls for heating or cooling are answered, and the unit will not respond to any commands. A failed transformer is often misdiagnosed as a control board failure, making this an essential first diagnostic step.
Compatibility: Designed specifically for the Carrier FY4ANF018008AAAA fan coil unit. Always confirm your existing transformer's VA rating and primary/secondary voltages on the unit data plate before ordering. Have questions about fitment? Our HVAC parts specialists verify compatibility before you buy — contact us any time.