Water heater runs but hot water temperature fluctuates between hot and cold.

Safety: Beware of sudden hot water temperature changes that can cause scalding.

• Check flow rate: Avoid running multiple hot outlets at once. Excessive flow can cause temperature swings.
• Clean inlet filters: Ensure both cold inlet and heating return filters are clean to maintain stable flow.
• Check mixer taps: Thermostatic mixer valves can fail and cause fluctuations; test with a simple two-handle tap if possible.
• Service required: If fluctuations persist, an engineer may need to descale or replace the plate heat exchanger and verify sensor readings.