The pressure switch is a safety device designed to prevent overheating of the spa heater should a low or no-flow condition exist in the spa. Electrical Operation The pressure switch is located in the heater circuit. When the switch is closed (proper flow), voltage is transferred to the heater circuit when the control thermostat calls for heat. Activating the relay allows the heater to activate. When the switch is open (low flow), voltage to the heater circuit is interrupted regardless of the state of the control thermostat. This prevents the heater from activating until the low flow condition has been resolved. WARNING: The pressure switch is a safety device and should never be bypassed or tampered with. Never attempt to calibrate the pressure switch. The following are some of the common causes of pressure switch tripping; Dirty or Clogged filters Clogged heater return Low Water level Removal Disconnect power to the spa. Remove the equipment compartment door. Drain the spa or use the plug system. Open the drain valve to bleed the water out of the plumbing. Open the control box lid. Disconnect the pressure switch connection wires from the pressure switch. Unscrew the pressure switch from the heater and remove any residual Teflon tape from the threads of the heater body where the pressure switch was connected. Reverse the removal procedure to install the pressure switch in the control box. NOTE: Wrap one piece of Teflon tape (in the opposite direction of the threads) three times around the pressure switch threads before installation. When screwing the new pressure switch into the heater, DO NOT use pliers, grasp the body of the pressure switch and hand tighten only. After you are finished with the installation, switch the jet pump to high speed and check the pressure switch for leaks.