GE Refrigerator Error Code F509

Error code F509 on a GE refrigerator indicates that the control board is detecting an input signal from the Hot Water Temperature and Pressure (T&P) switch at a time when that signal is not expected. The T&P switch is a safety-sensing component that monitors pressure or temperature conditions in systems where hot water is involved. When the control board receives a closed-circuit signal from this switch outside of normal operating parameters, it flags F509 to alert technicians that something in the switch circuit is outside expected behavior.

The most likely causes involve the T&P switch itself or the wiring connected to it. The switch may have failed in a closed position, sending a constant signal to the control board even when conditions do not warrant it. Alternatively, damaged, shorted, or pinched wiring in the switch circuit can create a false signal that mimics a closed switch state. Connector corrosion or moisture intrusion at the wiring harness terminals can also produce intermittent or persistent false inputs.

Diagnosis should begin with a visual inspection of the T&P switch and its associated wiring harness. Check for signs of physical damage, corrosion at connectors, or wiring that may have been pinched during installation or a previous repair. If the wiring appears intact, use a multimeter to test the switch for continuity in its resting state. A switch that shows continuity when it should be open indicates a failed component that requires replacement. Confirm the control board is receiving the correct signal only after the switch and wiring have been ruled out.