Controller displays HI or HIGH TEMP and shuts off solar heating even though the pool does not feel excessively hot.

Safety first: Turn off controller power before adjusting sensors or wiring. Use caution on hot roofs and avoid stepping on Heliocol panels.

• Confirm actual water temperature: Use a reliable pool thermometer to verify the real pool temperature. If it is normal, the issue is likely sensor-related.
• Inspect sensor placement: Ensure the solar sensor is strapped to a Heliocol header pipe, not lying directly on the roof surface or under the panel where temperatures can exceed design limits.
• Secure sensor: Use UV-resistant cable ties to firmly attach the sensor to the header, ensuring good contact but not crushing the sensor body.
• Check for cable interference: Route sensor wiring away from high-voltage pump wiring and relay coils to reduce electrical noise. Replace damaged or extended cables with shielded cable if recommended by the controller manufacturer.
• Replace suspect sensor: If readings remain abnormally high compared to actual temperature, replace the solar sensor with a compatible Heliocol-approved sensor.