L4
American Standard
Open Compressor Circuit / Contactor Fault
Indoor control board LED flashes L4 and the compressor does not start
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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 compressor contactor, Broken compressor lead, Open thermal overload inside compressor, Loose high-voltage connections in American Standard condensing unit
How to Fix / Troubleshooting
Safety first: Turn off power at the outdoor disconnect and main breaker. High voltage is present in this compartment.
- Inspect contactor: Remove the service panel and locate the contactor. Check for burnt or pitted contacts and loose wires. Replace the contactor if the contacts are severely worn or the coil is open.
- Check compressor terminals (visual only): Look for burnt or disconnected wires at the compressor terminal cover. Do not attempt to remove the cover unless you are qualified.
- Tighten lugs: With power off, tighten all high-voltage lugs on the contactor and line connections.
- Professional testing: If L4 persists, a technician should test compressor windings and continuity through the contactor and overload.
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Repair Difficulty
Professional Required
5/5
Required Part
Compressor Contactor
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