Coleman
Open Control Circuit or Failed Control Board
Thermostat clicks and calls for heat, but furnace does nothing.
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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
Broken W wire between thermostat and furnace, Failed relay on control board, Blown low-voltage fuse, Faulty thermostat not actually closing circuit under load
How to Fix / Troubleshooting
Safety first: Turn off power before moving thermostat wires.
Steps to check:
- Bypass thermostat: At the furnace control board, jumper R to W. If the furnace starts, the thermostat or its wiring is at fault.
- Check low-voltage fuse: Inspect and replace the 3–5A fuse on the control board if blown.
- Test W terminal: With a call for heat, measure 24 VAC between W and C at the furnace. If no voltage, the thermostat or wiring is open.
If the furnace does not respond even when R and W are jumpered, the control board is likely defective and should be replaced with a Coleman OEM board.
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Repair Difficulty
Medium
3/5
Required Part
Integrated Furnace Control Board
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