Gibson Low-Voltage Short or Transformer Overload

Thermostat goes blank when furnace tries to start

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.

Possible Causes

Shorted thermostat cable, Shorted humidifier or accessory wired to R and C, Failing 24V transformer on Gibson furnace, Miswired low-voltage connections

How to Fix / Troubleshooting

Safety first: Turn off furnace power before working on low-voltage wiring.

Steps to check:

Inspect thermostat cable: Look for staples driven through the cable or visible damage near the furnace and thermostat.
Disconnect accessories: Temporarily disconnect any humidifier, air cleaner, or other devices connected to the R and C terminals. Restore power and see if the thermostat stays on.
Check fuse: Replace the low-voltage fuse on the control board if blown. If it blows again, there is a short that needs professional diagnosis.

Repair Difficulty

Medium 3/5

Required Part

24V Transformer

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