Things You'll Need
Central Pneumatic makes a full line of air tools and compressors for sale by Harbor Freight tools. The 94667 is a 21-gallon upright tank compressor. Like all Central Pneumatic compressors, it has two pressure adjustments. The first is the outlet pressure and is governed by a pressure regulator on the control panel of the compressor. This is the pressure going from the compressor into your tools. The other adjustment is hidden under a plastic cover above the air regulator. It controls how high the pressure in the tank will rise, before the compressor shuts off, or "cuts out".
Turn the compressor on and allow it to charge the tank completely. Make note of the pressure on the gauge, located on the compressor's control panel. Look just above this and locate the plastic shroud covering the pressure switch. It will be a black plastic rectangular box. Remove the one screw on the left side and lift the plastic cover off.
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Look for the hex-head brass bolt on top of the switch. It is located just behind the yellow button, which pops up when the correct pressure is reached and can be depressed to kick the compressor on. Look for the plus and minus signs beside the bolt, they have arrows indicating the direction to turn the bolt head to achieve the desired result.
Turn the bolt clockwise with a wrench to raise the pressure setting, causing the compressor to run longer before it cuts out. Turn it counterclockwise to lower the pressure. Pull the release valve located directly below the pressure switch to release pressure and turn the compressor motor on. Make note of the pressure when the switch pops up and adjust the bolt as needed to get the desired pressure.
Reinstall the black plastic cover and insert the mounting screw into the hole. Turn it clockwise to tighten. Return the compressor to normal use.