Poolex pool heater intermittently shuts down with F7 error; may occur during very cold or hot weather.

How to Fix / Troubleshooting

Safety: Isolate electrical supply before removing any covers.

Inspection steps:

Find the evaporator sensor: It is usually clipped directly to the evaporator coil tubing or fins inside the unit.
Check attachment: Ensure the sensor is firmly clipped to the coil; a loose sensor can misread temperature and trigger F7.
Inspect cable: Look for chafing where the cable passes through metal panels. Repair or protect with conduit if needed.
Clean connectors: Disconnect and reconnect the sensor plug to clear oxidation.

Sensor replacement:

Obtain a genuine Poolex evaporator/anti-freeze NTC sensor.
Remove the old sensor from the coil and unplug it from the harness.
Install the new sensor in the same position and secure it firmly to the coil.
Restore power and test operation in heating mode.

If F7 persists, a technician should check sensor resistance vs. temperature and verify the main control board.