Description & Operation

The High Altitude Compensation (HAC) system adjusts air/fuel ratios to compensate for changes in altitude based upon barometric pressure. At altitudes above 3280 feet (where air pressure is reduced and air/fuel mixtures become richer), the compensator valve will open, allowing additional air to bleed into the fuel delivery system. At altitudes below 3280 feet, the compensator valve remains closed and air/fuel ratios are maintained by the Electronic Fuel Control (EFC) system.