E10
Trane
Low Voltage Power Fault
Thermostat displays E10 and system may not energize any outputs
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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
No 24 VAC between R and C from Trane transformer, Blown low-voltage fuse on indoor control board, Open transformer winding, Loose R or C wire at thermostat or control board
How to Fix / Troubleshooting
Safety warning: Turn off power to the air handler/furnace at the breaker before accessing internal components.
- Step 1 – Check HVAC power: Confirm the indoor unit breaker and service switch are ON and the blower door is properly closed.
- Step 2 – Measure voltage at thermostat: With power ON and using a multimeter, measure between R and C at the thermostat. If 0 VAC, proceed to the indoor unit.
- Step 3 – Inspect fuse: At the indoor control board, locate and check the low-voltage fuse. Replace if blown with the same rating. If it blows again, there is a short in the low-voltage circuit that needs professional diagnosis.
- Step 4 – Check transformer output: Measure between the transformer secondary leads (usually 24 VAC). If no voltage, replace the transformer.
- Step 5 – Tighten R and C connections: Ensure R and C wires are secure at both the thermostat and control board.
- Step 6 – Restore power and test: After repairs, restore power and verify that E10 clears and the thermostat powers normally.
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Repair Difficulty
Hard
4/5
Required Part
Trane Indoor Unit Transformer or Low-Voltage Fuse
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