Carb heat on the left side behind the trims. Check your carb heat gauge as well. You could be getting carb ice.
HOT AIR CONTROL LEVER. The Hot Air Control lever has two positions: NORMAL and HOT AIR. When set to NORMAL, the hot air door is closed and either ram air or unrammed filtered air enters the carburetor, depending on the Ram Air Control lever setting. When set to HOT AIR, the hot air door is open and warm air from the engine compartment enters the carburetor. Note, the warm air door is spring-loaded and will open automatically in case of icing or other foreign object obstruction due to the suction on the carburetor.