Zodiac pool heater shows E12; may be accompanied by erratic temperature readings or unexpected shutdowns.

Safety: Disconnect power before accessing sensors on the water manifold.

• Locate outlet sensor: Identify the outlet water temperature sensor on the heater header (often separate from the main water temperature sensor). Trace its wiring to the control board.
• Inspect and reseat: Unplug the sensor connector, inspect for corrosion or bent pins, and reconnect firmly.
• Measure resistance: With the sensor disconnected and power off, measure resistance and compare to Zodiac's temperature chart. Replace the sensor if readings are out of range or open/shorted.
• Check harness: Inspect the harness for cuts or abrasion where it passes through metal panels. Repair or replace as needed.
• Control board check: If a new sensor does not clear E12, the control board input may be faulty and require replacement.