Tappan Loss of 24V Power to Thermostat

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 Tappan control board, broken R or C wire to thermostat, failed 24V transformer

Safety: Turn off power before checking low-voltage wiring.

Steps:

Check the furnace control board fuse and replace if blown. If it blows again, look for shorts in thermostat wiring.
Inspect the thermostat cable for damage where it enters the furnace and at the wall.
Measure 24 VAC between R and C at the control board. If present but the thermostat is blank, the issue is in the cable or thermostat. If absent, test and replace the transformer as needed.

Medium 3/5

24V Control Transformer

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