F3
Marey Flow Switch / Flow Sensor Fault (Electric Model)

Marey electric tankless heater shows F3; unit may not energize heating elements.

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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

Stuck mechanical flow switch, Defective electronic flow sensor, Clogged inlet filter reducing flow below activation threshold

How to Fix / Troubleshooting

Safety first: Turn OFF power at the breaker and close the water supply. Allow the unit to cool.

Steps:

  • Clean inlet filter: Remove the cold inlet connection and clean the mesh filter screen.
  • Check flow switch: Open the cover and locate the flow switch or sensor on the inlet. For mechanical switches, gently move the paddle or plunger to ensure it is not stuck. For electronic sensors, inspect for scale buildup.
  • Verify minimum flow: Restore water and open a hot tap fully. Many Marey electric units require a minimum flow to activate; remove low-flow aerators if necessary.
  • Replace faulty switch/sensor: If the switch does not change state or the sensor does not signal flow (requires meter), replace the flow switch assembly.

When to call a technician: If internal wiring or control board issues are suspected.

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Repair Difficulty

Medium 3/5

Required Part

Flow Switch / Flow Sensor (Marey electric inlet assembly)
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