F3 means that your water temperature was sensed at greater than 85°C ( 185°F)
First, check to see if the incoming water temperature is greater than 85°C (185°F). If the temperature is too hot, you need to turn your hot water heater down, otherwise remove the dish rack and take out the wash arm. Unlock the center locking nut to access the rotor and metal plate heater around the rotor (you can look in the dishwasher video section to see how to take apart these Fisher and Paykel Dishwashers) Touch the heater and is it hot all the time? If so, replace the electronic controller in the upper right hand corner of the dish drawer.
If the heater is cool and your water is not coming in too hot, check the wires between the control board and the heater under your dish drawer. A F&P wire harness tends to burn and cause these F3 errors. Replace the wire harness if the wires are damaged. If the wires check good, check the resistance of the heating sensor under the drawer. As a last resort, replace the heater plate since it’s the only part that can not be tested.