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This is the factory OEM replacement control transformer (part# HT01CN001) for the Carrier GB1AAV036045AGJA gas furnace. The transformer steps down line voltage from 120V to 24V to power the low-voltage control circuit — including the thermostat, control board, gas valve, and contactor coil. When it fails, the entire control circuit goes dark: the thermostat display goes blank, the system refuses to respond to any call for heat or cooling, and you may detect a burning or overheated odor near the air handler cabinet.
Compatibility: Designed specifically for the Carrier GB1AAV036045AGJA gas furnace. Verify your existing transformer's VA rating and primary/secondary voltage on the data plate or old transformer label before ordering — mismatched VA ratings can damage the control board. Need fitment confirmation? Our parts team is available to verify compatibility before you buy.