Concord
No Call for Heat Reaching Furnace
Furnace will not start at all; thermostat appears to be working but there is no response from the furnace.
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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 wire, Faulty thermostat, Blown low-voltage fuse on control board, Open float switch on condensate line (high-efficiency models)
How to Fix / Troubleshooting
Safety: Turn off power before working on low-voltage wiring.
Steps:
- Check 24V fuse: Inspect and replace the low-voltage fuse on the Concord control board if blown.
- Test R to W: At the furnace, jumper R and W terminals briefly with a small piece of wire. If the furnace starts, the problem is in the thermostat or thermostat wiring.
- Inspect condensate safety: On condensing models, check any condensate float switch in the drain line. If the drain is clogged, the switch may open and prevent operation. Clear the drain and reset the switch.
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Repair Difficulty
Medium
3/5
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