E99
Rheem
Lockout Due to Repeated Ignition or Safety Failures
Rheem tankless water heater shows E99 and locks out
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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
Multiple unresolved ignition errors, Persistent overheat or flame errors, Control board safety lockout
How to Fix / Troubleshooting
Safety first: Identify and correct the underlying cause before clearing lockout.
- Review history: Note any previous error codes (E11, E12, E13, etc.) that occurred before E99.
- Correct root cause: Address gas supply, venting, ignition, or overheat issues as indicated by earlier codes.
- Reset lockout: Turn OFF power for at least 10 minutes, then restore. Some models may require a specific reset sequence via the control panel.
- If E99 returns: Do not continue resetting. Have a qualified technician perform a full diagnostic.
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Repair Difficulty
Hard
4/5
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