Step 1
Use the wrench to turn the bolt that fastens the cover on the switch counterclockwise, and pull off the cover. This is the only bolt on top of the cover.
Step 2
Turn the large bolt clockwise to increase the pressure. The pressure adjustment mechanism is the large bolt located inside the pressure switch with a spring underneath it. For each complete turn, the pressure is adjusted in 2.5 PSI increments.
Step 3
Turn the large bolt counterclockwise to reduce the pressure.
Step 4
Place the cover back on the switch, and tighten the bolt to secure it.