E17
Alpha Supply Air Temperature Sensor Fault

Furnace shows E17; unit may run at reduced capacity or shut down intermittently.

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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

Open or shorted supply air thermistor, Loose sensor harness to Alpha control board, Sensor out of calibration, Control board input failure

How to Fix / Troubleshooting

Safety: Turn off power before accessing the supply plenum or sensor wiring.

  • Locate sensor: Find the supply air temperature sensor mounted in the supply plenum or on the furnace outlet.
  • Inspect wiring: Ensure the sensor leads are intact and the connector is firmly seated on the control board.
  • Check for physical damage: Replace the sensor if the probe is broken, corroded, or has damaged insulation.
  • Power reset: After reseating or replacing the sensor, power the furnace back on and test operation.

If E17 remains, the control board's sensor circuit may require replacement.

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Repair Difficulty

Medium 3/5

Required Part

Alpha Supply Air Temperature Sensor
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