As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING THE RUN UP PRIOR TO FLIGHT, THE PILOT REALIZED THAT THERE WAS NO RESPONSE WHEN APPLYING CARBURETOR HEAT TO THE LT ENGINE. ACFT WAS SNAGGED. MAINTENANCE FOUND THE LEVER THAT ATTACHES TO THE VALVE INSIDE THE CARB AIR BOX HAD SEPARATED WHERE THE ARM WAS WELDED TO THE SHAFT. MAINTENANCE REPLACED THE VALVE WITH A SERVICEABLE ONE.