Locate the temperature sensor assembly shown above. The sensor is installed inside the black rubber nut and reads the spa water temperature as it flows into the circulation pump. On some spas, it is easy to perform these steps. On others, the sensor assembly is behind other equipment making the job a little tougher.
If debris builds up on the right side of the sensor, it can form a partial dam and block water flow into the pump, causing a flow message.
Using your fingers, remove the silicone seal.
Using a crescent wrench, unscrew the rubber nut 2 full turns. Do not remove the nut from its white housing.
Carefully lift the sensor about 3/4″. Do not remove the sensor from the rubber nut.
Remove the cork at the end of this hose for about 5 seconds to let the water flow flush out debris. Using a 12″ piece of wire (or piece of a coat hanger), carefully push the wire into the fitting about 8-10″. This may loosen any debris caught further up the white fitting assembly. Replace the cork.
Push the sensor back into place until it is level with the top of the black rubber nut.
Tighten the rubber nut 2 full turns; more if necessary, to stop any water drips.
Put a bead or pile of silicone in place to prevent water leaks from the sensor/nut seam.
Replace the circulation pump assembly. You have now cleared any obstruction in the circulation pump and temperature sensor assembly. If this was the cause of the “Flow” error, the spa will begin heating when you turn the power back on.
Replace access panel door.