High Altitude COMPENSATOR (HAC): Federal
- Disconnect Yellow-striped vacuum hose from HAC. Connect vacuum pump to HAC. At low altitude, 3900 ft. (1200 m) or less, when vacuum is applied, vacuum should leak. At high altitude, vacuum should hold.
- On low altitude vehicles, disconnect Red-striped hose from HAC and connect vacuum pump. Vacuum should hold when applied. On high altitude vehicles, disconnect Red-striped hose from HAC and connect another vacuum pump. Hold vacuum with first pump, and apply vacuum with second pump. Vacuum should leak when applied.