Controller displays Er1 and solar heating is disabled.

Safety: Turn off power to the controller before handling sensor wiring.

• Check terminals: Open the controller and verify the pool sensor wires are firmly clamped in the correct terminals.
• Inspect cable: Follow the sensor cable from the controller to the plumbing. Look for cuts, pulled connections, or rodent damage.
• Test sensor: Disconnect the sensor and measure resistance with a multimeter. An infinite reading indicates an open sensor that must be replaced.
• Replace sensor: Install a new Fafco pool temperature sensor in the existing well or saddle, route the cable neatly, and reconnect to the controller.