[Image of a schematic diagram showing the vacuum lines for the 1974 Corvette headlights]
Key:
* 1: Vacuum source (carburetor)
* 2: Check valve
* 3: Headlight vacuum switch
* 4: Headlight vacuum motor
* 5: Headlight vacuum actuator
Operation:
1. When the engine is running, vacuum is supplied from the carburetor to the vacuum source (1).
2. The check valve (2) allows vacuum to flow to the headlight vacuum switch (3), but prevents vacuum from flowing back into the carburetor.
3. When the headlight switch is turned on, the headlight vacuum switch (3) opens, allowing vacuum to flow to the headlight vacuum motor (4).
4. The headlight vacuum motor (4) opens the headlight vacuum actuator (5), which turns on the headlights.
Note:
* The headlight vacuum switch is located on the firewall, near the brake master cylinder.
* The headlight vacuum motor is located on the back of the headlight assembly.
* The headlight vacuum actuator is located inside the headlight assembly.
