Bosch
Partial Heating Element Failure
Bosch electric tankless water heater runs but water is only slightly warm
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Safety Warning
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.
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Possible Causes
One or more heating elements burned out, Failed triac or relay on control board, Loose wiring to element terminals, Incorrect power supply voltage
How to Fix / Troubleshooting
Safety first: Turn OFF power at the breaker and verify with a meter that power is off before touching internal components.
- Check supply voltage: Confirm that the heater is supplied with the correct voltage (e.g., 240 V) using a multimeter at the junction box.
- Inspect wiring: Remove the cover and check that all element terminal screws are tight and wires are not burned.
- Test elements: Disconnect each heating element and measure resistance with a multimeter. Replace any element that is open or significantly out of specification.
- Control board: If all elements test good but some do not energize, the control board's switching devices may be faulty and require replacement by a technician.
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Repair Difficulty
Hard
4/5
Required Part
Heating Element Assembly
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