E8
Ruud
Fan Speed / Combustion Feedback Error
Tankless water heater displays E8; unit may run at reduced output or shut down.
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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
Faulty fan speed sensor (Hall effect sensor), Loose fan harness connection, Obstructed fan wheel, Defective main control board fan circuit
How to Fix / Troubleshooting
Safety first: Turn OFF power and gas before removing covers.
- Step 1 – Inspect fan harness: Remove the front cover and locate the combustion blower. Check the small multi-wire connector from the fan to the control board. Reseat it firmly.
- Step 2 – Check for obstructions: Inspect the fan wheel for debris or damage. Ensure it spins freely by hand.
- Step 3 – Reset and test: Restore power and gas, then run hot water. If E8 returns, the fan sensor or board may be faulty.
- Step 4 – Replace fan assembly: Many Ruud fan speed sensors are integrated into the blower. With power and gas OFF, remove the blower assembly and install a new OEM Ruud combustion blower. Reconnect wiring and reassemble.
If a new blower does not resolve the issue, the main control board likely needs replacement by a professional.
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Repair Difficulty
Hard
4/5
Required Part
Combustion Blower Assembly
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