F2
Fraser-Johnston
Evaporator Coil Temperature Sensor Fault
F2 error, unit may short cycle or not maintain set temperature
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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
Failed evaporator thermistor, Sensor not properly attached to coil, Damaged sensor wiring, Faulty indoor control board sensor circuit
How to Fix / Troubleshooting
Safety: Disconnect power at the breaker before accessing the coil compartment.
- Find the sensor: The evaporator thermistor is clipped to the copper tubing of the indoor coil on Fraser‑Johnston units.
- Check mounting: Ensure the sensor is firmly clipped to the coil and has good thermal contact. Reattach if loose.
- Inspect wiring: Look for nicks, cuts, or pulled wires along the sensor harness. Repair or replace as needed.
- Measure resistance: Compare sensor resistance to the temperature chart. Replace if out of range.
- Board check: If a known-good sensor still gives F2, the indoor PCB may have a defective sensor input and require replacement.
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Repair Difficulty
Medium
3/5
Required Part
Evaporator Coil Thermistor
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