F15
Whirlpool
Tank Thermistor Fault
F15 error code, hybrid water heater indicates tank temperature sensor fault (upper or lower)
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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 tank thermistor, sensor not fully inserted into well, water intrusion into sensor, damaged harness to control
How to Fix / Troubleshooting
Safety first: Turn OFF power at the breaker.
Sensor verification:
- Locate the upper and lower tank sensors (often inserted into wells near the elements).
- Remove each sensor and inspect for corrosion, swelling, or moisture.
- Measure resistance at room temperature and compare to Whirlpool's specified values.
- Check harness continuity from sensor connector to the control board.
Corrective actions:
- Replace any sensor with out-of-spec resistance or visible damage.
- Ensure sensors are fully seated in their wells and that insulation is replaced to prevent ambient influence.
- If wiring and sensors are good, replace the main control board.
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Repair Difficulty
Medium
3/5
Required Part
Upper Tank Thermistor / Lower Tank Thermistor
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