5
Rheem
Flame Sensed with Gas Valve Off / False Flame Signal
Status LED flashes 5 times; furnace shuts down and may lock out after several attempts
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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
Shorted flame sensor to ground, Faulty control board flame circuit, Induced flame rollout, Miswired burner ground
How to Fix / Troubleshooting
Safety first: Turn off power and gas. False flame detection can indicate serious combustion issues.
- Inspect flame sensor wiring: Locate the flame sensor rod and its wire back to the control board. Look for damaged insulation, bare spots touching metal, or loose connections. Repair or replace damaged wiring.
- Clean flame sensor: Remove the sensor and gently clean the rod with fine steel wool. Reinstall and ensure it is properly positioned in the burner flame path.
- Check burner ground: Verify that the burner assembly and furnace chassis have a solid ground connection to the electrical system. Tighten loose ground screws.
- Observe ignition sequence: With panels on and power restored, watch through the sight glass. If the board detects flame before the ignitor glows or gas valve opens, the control board may be defective and require replacement.
If you see flames outside the burner area or signs of rollout (scorching, melted wiring), shut down the furnace and call a professional immediately.
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Repair Difficulty
Professional Required
5/5
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