The controller displays 'Er3'; temperatures shown are unrealistic, and the system may behave erratically.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Shorted pool or roof sensor leads, Water intrusion into the sensor junction box, Crushed sensor cable, Miswired sensor terminals

Safety: Disconnect power to the controller before testing wiring.

Identify sensor: Consult the Fafco manual to determine whether 'Er3' refers to the pool or roof sensor.
Inspect for shorts: Look for pinched cable under clamps, water-filled junction boxes, or bare conductors touching.
Measure resistance: Disconnect the suspect sensor and measure its resistance. A near-zero reading indicates a shorted sensor.
Correct wiring: Ensure that the sensor leads are not crossed or touching other terminals inside the controller.
Replace sensor or cable: If the sensor itself is shorted, install a new Fafco-compatible sensor and reroute the cable to avoid damage.

Medium 3/5

Fafco Temperature Sensor Harness

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