Navien No Power / Electrical Supply Failure

Navien water heater will not power on at all; display is blank and unit appears dead.

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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

Tripped circuit breaker, Blown internal fuse on PCB, Loose power connection at terminal block, Failed main control PCB power supply section

How to Fix / Troubleshooting

Safety: Turn OFF the breaker before opening the unit. Verify power is off with a non-contact tester if available.

Steps:

  • 1. Check breaker and outlet: Verify the circuit breaker is ON and not tripped. Test the outlet or hardwired circuit with another device or a meter.
  • 2. Inspect power wiring: Remove the front cover and check that the power wires are securely connected to the terminal block and that there are no burnt or loose wires.
  • 3. Internal fuse: Many Navien PCBs have an internal fuse. Visually inspect for a blown fuse (darkened or broken element). Replacement should match the exact rating and be done with power OFF.

If the fuse blows again immediately or the unit remains dead, the PCB or internal power supply is likely faulty and requires professional replacement.

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Repair Difficulty

Medium 3/5

Required Part

Main Control PCB
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