C 10 1/2 Ton Pickup 2WD V8-379 6.2L DSL VIN C FI (1982)
Brake Switch (Cruise Control): Testing and Inspection
Disconnect vacuum hose from valve and connect a suitable vacuum pump with an integral gauge to valve.
With pedal in released position, apply approximately 14 inches of vacuum to valve, then observe gauge.
If valve loses more than 5 inches of vacuum in one minute, valve is defective.
With vacuum applied to valve, depress pedal. If valve does not release vacuum when pedal is depressed, valve is defective.