L5
American Standard
Line Voltage Polarity / Ground Fault
Indoor control board LED flashes L5 and the system shuts down shortly after starting
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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
Incorrect line voltage wiring, Open neutral, Poor equipment grounding, Faulty American Standard control board sensing circuit
How to Fix / Troubleshooting
Safety first: This involves line voltage diagnostics. If you are not experienced with electrical work, contact a licensed electrician or HVAC technician.
- Check breaker panel: Ensure the breakers feeding the indoor and outdoor units are properly installed and not double-tapped or loose.
- Inspect service disconnects: Verify that the disconnects are correctly wired and that there are no burnt or loose connections.
- Grounding: Confirm that the equipment ground wire is securely attached to the cabinet and ground bar.
- Professional meter checks: A technician should verify correct voltage, polarity, and grounding at the equipment terminals. If all is correct, the control board may be faulty.
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Repair Difficulty
Professional Required
5/5
Required Part
Indoor Control Board
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