Junkers Short Cycling / Minimum Power Too High for Flow

Heater cycles on and off rapidly with very short burner runs, even at a single tap.

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

Flow below minimum stable rate, Oversized heater for small demand, Faulty modulation control, Scale reducing heat transfer

Safety: Rapid cycling can reduce component life but is not usually immediately dangerous.

Increase flow: Open the tap more to increase flow and stabilize operation.
Adjust temperature setting: Lower the set temperature so the heater does not need to cycle as aggressively.
Descale: Have the heat exchanger descaled to improve heat transfer and reduce overshoot.
Check modulation: A technician can verify that the gas valve modulates down to minimum power correctly.

Medium 3/5

Gas Valve / Primary Heat Exchanger

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