Many air tools, such as nail guns, require pressures exceeding 100 pounds per square inch in order to function at full capacity. Compressors are governed by a limiter switch that gauges when the compressor turns on and at what point it will shut off. Adjusting this shut off, or upper limit, point, you can increase the pressure in your tank. Consult the manual or the maker of your compressor to find out what the upper limit can safely be before attempting to adjust it.
Use a screwdriver to remove the screws from the top of the pressure limiter switch cover. This is typically a plastic, vented cover on top of the compressor. Usually it is mounted with only one screw in the center, but some have four--one in each corner. Lift this plastic cover away from the compressor.
Locate the two limiter switch screws. The one closest to the switch, which has a brass spring curving up out of it, is the upper limit adjustment screw. Turn this screw clockwise to raise the limit.
Turn the compressor on and adjust the screw until the compressor runs until the gauge reaches the desired pressure. To maintain a higher pressure, turn the lower limiter adjustment screw, located beside the upper limiter adjustment screw. Turn this clockwise to raise it so that the compressor kicks on sooner, before the pressure drops too low to be useful.
Leave the cover off. Connect the tool you use most and charge the compressor. Test the limit you have set by using the tool and making the needed adjustments to these two screws. Replace the cover and tighten the screws to hold it in place.