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FlowMax · Combi boiler

E05 Heating (supply) sensor fault

Medium severity FlowMax condensing combi (FLOWMAX-90/120)

What the control is telling you

The heating NTC sensor reads out of range. Sensor is 10 kOhm at 25°C (77°F). Note: the 120 troubleshooting table text is misaligned in this area; meaning is taken from the diagnostics list and user manual.

Applies to: FLOWMAX-90, FLOWMAX-120

Likely causes

  • Sensor faulty or out of calibration
  • Sensor wire disconnected or wet

Test and repair steps

  1. Turn off power before working on sensor wiring.
  2. Check the sensor connector and wiring for looseness, damage or moisture.
  3. Unplug the sensor and measure resistance about 10 kOhm at 25°C (77°F).
  4. Replace the sensor if the reading is open, shorted or far off.
  5. Restart and confirm the code clears.

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Source: FlowMax FLOWMAX-120 Instruction Manual, 6.10 Troubleshooting table, p.66; FlowMax FLOWMAX-120 Instruction Manual, 6.11 Diagnostics error code list, p.67; FlowMax FLOWMAX-90 User Manual, Diagnostics - Error codes, p.8-9. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.