15
Ruud
Booster Fan / Secondary Fan Fault (on some models)
Ruud tankless water heater shows error code 15; unit may run at limited capacity 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
Failed booster fan motor, Loose booster fan wiring, Blocked venting, Control board fan driver fault
How to Fix / Troubleshooting
Safety first: Turn OFF power and gas before servicing.
- Step 1 – Inspect venting: Ensure vent pipes are not blocked or crushed and terminations are clear.
- Step 2 – Check booster fan wiring: Remove the front cover and locate the booster fan (if equipped). Verify connectors are secure and wires undamaged.
- Step 3 – Listen for fan operation: Restore power and call for hot water. If the booster fan does not run when expected, turn power OFF again.
- Step 4 – Replace booster fan: Disconnect wiring, remove mounting screws, and install a new OEM Ruud booster fan assembly. Reassemble and test.
If the new fan does not resolve the issue, the control board may need replacement by a professional.
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Repair Difficulty
Hard
4/5
Required Part
Booster Fan Assembly
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