Trane
No Thermostat Power / Control Circuit Failure
Trane air conditioner will not start; thermostat is blank or unresponsive.
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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
Blown low-voltage fuse on indoor board, Tripped float switch in condensate line, Broken R wire to thermostat, Failed thermostat
How to Fix / Troubleshooting
Safety first: Turn off power to the indoor unit before accessing the control board or float switch.
- Check low-voltage fuse: Inspect and replace the 3–5A fuse on the Trane control board if blown.
- Inspect float switch: Locate the condensate safety switch on the drain line or pan. If tripped due to water, clear the drain and reset or dry the switch.
- Thermostat power: Confirm 24VAC between R and C at the thermostat. If absent, trace the R wire back to the control board for breaks.
- Replace thermostat: If power is present but the thermostat remains blank, replace it with a compatible Trane or universal thermostat.
If the fuse blows repeatedly, there is a short in the low-voltage wiring that must be located and repaired.
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Repair Difficulty
Medium
3/5
Required Part
Trane Low-Voltage Fuse
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