Trane Loss of 24V Control Power

Thermostat display is blank and furnace does not run

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

Blown low-voltage fuse on furnace board, Shorted thermostat wire, Failed 24V transformer, Loose R or C connections

Safety: Turn off furnace power before checking the control board.

Steps to check:

Board fuse: Inspect the automotive-style fuse on the Trane control board and replace if blown.
Thermostat wiring: Look for bare thermostat wires touching each other or metal.
Transformer output: With a multimeter (advanced), verify 24V between R and C at the board.

When to call a professional: If the fuse keeps blowing or no 24V is present, a technician should locate the short or replace the transformer.

Medium 3/5

24V Control Transformer

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