E18
Kospel Outdoor Temperature Sensor Fault (if equipped)

Furnace shows E18; may be accompanied by erratic temperature readings or frequent cycling.

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Possible Causes

Failed outdoor NTC sensor, Broken sensor cable, Incorrect sensor placement, Corroded terminal connections

How to Fix / Troubleshooting

Safety: Turn off power before connecting or disconnecting the outdoor sensor.

  • Locate outdoor sensor: It is usually mounted on an external north-facing wall away from direct sun.
  • Inspect cable: Check for cuts, UV damage, or loose junction box connections.
  • Test sensor: Measure resistance and compare with Kospel's NTC chart. Replace if out of range.
  • Check controller settings: Ensure weather-compensation is configured correctly in the Kospel control menu.
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Repair Difficulty

Easy 2/5

Required Part

Outdoor Temperature Sensor
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