A.O. Smith 110-310-510 – CHECKING THE OVERHEAT CUTOFF FUSE (OHCF):

1) Locate the white OHCF which wraps around the heat exchanger.
2) Find the white clip at the end of the two blue braided wires coming from the OHCF.
3) Unplug the connection.
4) Test for continuity at the end of the OHCF with an ohmmeter. If there is continuity, the OHCF is still intact. Reconnect the plug. If there is no continuity, the OHCF has been compromised. If compromised, contact the Technical Service Department for further assistance.
5) If an ohmmeter is not available, jump the plug connection on the opposite side of the OHCF with a wire, paper clip, or other metal material.
6) Restore power and test unit. Be very cautious with this step. Do not touch the jumper or other electrical components.
7) If the unit fires up, it shows that the OHCF has been compromised and the problem was with the OHCF. If so, contact the Technical Service Department for further assistance. If the unit does not fire up, it shows that the cause of the 111 or 121 error code is something else. Continue with the 111 or 121 error code sections of this guide for further troubleshooting.

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