F7
Trane Phase Loss / Phase Reversal (Three-Phase Units)

Trane air conditioner shows F7 and may not start; fan may run but compressor stays off.

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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

Missing phase from power supply, Incorrect phase rotation, Loose power lugs, Faulty phase monitor relay

How to Fix / Troubleshooting

Safety first: Three-phase systems carry dangerous voltages. Only qualified personnel should work inside the high-voltage compartment.

  • Check breakers: Verify all three-pole breakers feeding the Trane condenser are ON and not tripped.
  • Inspect lugs: With power off and locked out, tighten all line and load lugs at the contactor and disconnect.
  • Phase monitor: If equipped, check the phase monitor relay indicator. A fault indication may require an electrician to correct incoming power or replace the relay.

Phase issues must be corrected by a licensed electrician or HVAC technician familiar with three-phase Trane equipment.

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Repair Difficulty

Professional Required 5/5

Required Part

Trane Phase Monitor Relay
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