E17
Lochinvar
Differential Temperature / Sensor Mismatch Fault
Display shows E17; heater 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
Mismatched inlet and outlet sensors, Poor sensor placement in plumbing, Control calibration error
How to Fix / Troubleshooting
Safety: Turn off power before working on sensors.
Steps:
- Verify sensor types: Ensure both inlet and outlet sensors are the correct Lochinvar parts for your model; mixing sensor types can cause errors.
- Check sensor installation: Sensors must be fully inserted into the header or well with good thermal contact. Re-seat any loose sensors.
- Compare readings: With the heater off and water circulating, inlet and outlet temperatures should be similar. Large differences at rest indicate a sensor issue.
If sensors are correct and properly installed, a technician may need to recalibrate or replace the control board.
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Repair Difficulty
Hard
4/5
Required Part
Inlet/Outlet Temperature Sensors
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