F1
Frigidaire 24V Transformer or Low-Voltage Power Fault

Furnace control flashes F1; unit may not respond to thermostat

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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

Failed 24V transformer, Shorted thermostat wiring, Blown low-voltage fuse, Loose low-voltage connections

How to Fix / Troubleshooting

Safety: Turn off power before accessing the control compartment.

  • 1. Check low-voltage fuse: Inspect and replace the 3–5A fuse on the control board if blown. If it blows again immediately, there is a short in the 24V circuit.
  • 2. Inspect thermostat cable: Look for damaged or pinched thermostat wires where they enter the furnace cabinet and along visible runs. Repair or replace damaged sections.
  • 3. Disconnect external circuits: Temporarily disconnect thermostat wires at the furnace, leaving only R and C connected. If the fuse holds, reconnect circuits one at a time to find the shorted run.
  • 4. Transformer check: If there is no 24V between R and C with a good fuse, the transformer may be failed and should be replaced with a Frigidaire-rated 24V transformer by a technician.
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Repair Difficulty

Medium 3/5

Required Part

24V Control Transformer
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