Ideal
Thermostat Control / Low-Voltage Circuit Fault
Furnace will not respond to thermostat; thermostat appears to work but furnace stays off
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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 thermostat cable, loose R or W connection at Ideal control board, blown low-voltage fuse, incompatible thermostat
How to Fix / Troubleshooting
Safety: Turn off power before working on low-voltage wiring to avoid shorting the control board.
Steps:
- Thermostat batteries: Replace batteries if the thermostat uses them.
- Check wiring: Remove the thermostat and verify that wires are firmly attached to the correct terminals. At the furnace, check that R and W are secure on the control board.
- Fuse check: Inspect the low-voltage fuse on the Ideal control board and replace if blown with the same rating.
- Bypass test: For a quick test, with power off, temporarily connect R and W at the furnace. Restore power; if the furnace starts, the thermostat or its cable is faulty.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat
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