Junkers Insufficient Heating / Underfiring

Water heater ignites but hot water is only lukewarm even at maximum temperature setting.

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

Low gas pressure, Partially blocked burner injectors, Incorrect gas type or nozzle, Modulation valve not opening fully

Safety: Gas adjustments must be done by qualified personnel.

Reduce flow: Slightly close the hot tap to reduce flow and increase outlet temperature. If temperature improves, the heater may be undersized or underfiring.
Check gas supply: Ensure other gas appliances are not causing major pressure drops when used simultaneously.
Clean aerators: Remove and clean tap aerators to ensure proper flow characteristics.
Professional gas check: Have a technician verify gas type, pressure, and burner injectors, and adjust combustion.

Hard 4/5

Main Burner / Gas Valve

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