Display shows A15, furnace may shut down on high temperature or fail to modulate correctly
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Do not bypass high-limit devices. Turn off power before inspection.
- Locate high-limit stat: Typically mounted on the heat exchanger or supply air plenum. Check for manual reset button and press if tripped after cooling.
- Inspect wiring: Ensure spade connectors are tight and wires are not overheated or brittle.
If A15 persists with a reset and good wiring, the limit stat should be replaced. If a new stat does not resolve the issue, the control board may be faulty and requires professional diagnosis.
Repair Difficulty
Required Part
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