E16 displayed, unit reports a sensor short circuit.

Safety: Isolate power before handling any wiring.

Steps:

• Identify which sensor: The manual or fault list on the casing should indicate whether E16 refers to the flow, return, or store sensor.
• Inspect cable route: Look for areas where the sensor cable is pinched under covers or cable ties. Free the cable and check for damage.
• Connector check: Disconnect the sensor from the PCB and inspect for moisture or corrosion. Dry thoroughly and refit if sound.
• Resistance test: Measure the sensor resistance. A reading near 0Ω indicates a shorted sensor; replace it.

After repair: Clear the error by power-cycling and confirm stable temperature readings in normal operation.