L2
American Standard
Low-Voltage Short / Fuse Open
Indoor control board LED flashes L2 and the system will not respond to thermostat calls
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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
Shorted thermostat cable, Shorted outdoor contactor coil, Miswired accessory (humidifier, UV light) on R and C, Blown 3A/5A fuse on American Standard control board
How to Fix / Troubleshooting
Safety first: Turn off power to the indoor unit before replacing fuses or inspecting wiring.
- Inspect low-voltage fuse: Locate the blade fuse on the indoor control board. If blown, replace with the same amperage rating only.
- Isolate the short: If the new fuse blows immediately, disconnect thermostat wires at the board and replace the fuse again. If it holds, the short is in the thermostat cable or connected devices.
- Check thermostat cable: Inspect the cable along its run for damage. Remove the thermostat and check for bare wires touching. Repair or replace as needed.
- Inspect outdoor contactor coil: Disconnect the two low-voltage wires at the outdoor contactor. If the fuse no longer blows, the contactor coil may be shorted and should be replaced.
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Repair Difficulty
Medium
3/5
Required Part
Low-Voltage Fuse
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