Controller displays ERR or ERROR with no additional code and solar heating is locked out.

Safety first: Turn off power at the breaker before opening the controller. Use caution around live circuits.

• Check supply voltage: Measure the input voltage to the solar controller and confirm it matches the nameplate rating (typically 24 VAC or 120 VAC depending on model). Correct any wiring errors.
• Disconnect peripherals: With power off, disconnect sensors and valve actuator from the controller. Restore power and see if the ERR code clears. If it does, reconnect devices one at a time to identify the faulty component.
• Inspect board for damage: Look for burn marks, swollen capacitors, or cracked solder joints on the controller PCB. If present, the board likely needs replacement.
• Reset controller: Some models have a reset button or procedure (e.g., holding specific keys at power-up). Perform a reset according to the manual.
• Replace controller if needed: If the error persists with all external devices disconnected and correct voltage present, replace the solar controller with a compatible Heliocol-approved unit.