E004MEDIUM

NTC Thermistor Error (Navien)

Navien boiler temperature sensor (NTC thermistor) is reading outside the valid range.

What This Error Code Means

A temperature sensor circuit has failed, providing inaccurate temperature readings to the control board.

Common Causes

  • Sensor wiring damaged
  • NTC thermistor failed
  • Loose connection at PCB
  • Water ingress in sensor
  • Sensor reading open or short circuit

Affected Brands

Navien

How ROMA Heating Fixes This

  • Check sensor wiring and connections
  • Measure sensor resistance value
  • Compare reading to expected temperature curve
  • Replace failed NTC sensor
  • Verify accurate temperature readings after repair

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Licensed Technicians

TSBC Gas License LGA0202903. Fully insured and WCB covered.

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Seeing Error Code E004?

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