The Corvette C3 series is a sports car produced by the Chevrolet division of General Motors. The C3 was produced from 1968 through 1982 and is known among Corvette enthusiasts as "The Shark." GM installed vacuum-activated, pop-up headlights that were prone to wear out and leave the headlights stuck either open or shut.
The vacuum system was both vulnerable and complicated. Over time, the rubber hoses and other components of the vacuum system wear out, resulting in lost vacuum pressure in the headlight actuators, which open and close the headlamp doors. Oftentimes, only one headlight would operate, giving the impression that the Corvette was "winking." The owner either has to pry the headlight open or force it to shut.
To test whether or not the vacuum has failed or has a leak (with the headlamps in the open and locked position), disconnect the large green hose and attach the vacuum pump. If vacuum pressure holds, the internal diaphragm and rear sealing grommet are both good. If the vacuum pressure drops, replace the grommet. Rubber kits to rebuild the actuators are available at Corvette parts stores. With headlamps in the closed position, disconnect the large red hose and attach the vacuum pump. If the vacuum pressure holds, the internal diaphragm is good. If the vacuum pressure drops, the internal diaphragm is leaking and the actuator must be replaced.
Due to the headaches resulting from fixing a worn out vacuum system, many Corvette C3 owners decide to replace the pop-up head lights with fixed, recessed ones. Simple conversion kits are sold at car expos and Corvette supply catalogs.
