Abstract: A measuring head for an air pressure gauge having a movable actuating rod and capable of obtaining the car power source from the cigarette lighting socket is provided. The measuring head includes an insulating head tube having a through hole, a conductible actuating rod having an intermediate annual flange and an upper portion protruding beyond the through hole, a conductible plug having an axial through hole, a spring mounted between the plug and the annular flange for tightly urging the flange against the tube, and a conductible sleeve sleeved on the tube and connecting thereto a conducting wire.

Abstract: A gauger for a car includes a housing having a tubular receiving room, a gauge head having an air inlet and an axial projection capable of being urged against a car air valve, a pressure-measuring plunger slidably received in the receiving room, a piston engaging with the plunger for being forced by an air pressure to protrude plunger from the receiving room, an elastic member mounted for returning the piston to rest against the gauge head when the projection is removed from the air valve, two conducting members respectively mounted on the gauge head, and a circuit device electrically connected to the conductive members and capable of showing an electrical power state of a car battery. Such gauger is also designed to detect the wearing degree of a tire tread.