Verifying Functionality Of Computer Board, Displaying Error Code History, And Clearing Error Code History Memory - A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual

12-2. Verifying functionality of computer board, Displaying error code history,
and Clearing error code history memory
A. Check if the computer board works properly
Check the 100 VAC power supply on the computer board. Refer to part "A" on p. 11. Check the
voltage at "A". (Black-White)
If no voltage is detected going into the computer board, the fuse box or transformer might have
malfunctioned or been damaged.
If 100 VAC is measured going into the computer board and the water heater does not work, the
computer board or flow sensor might have malfunctioned or been damaged.
NOTE: When the flow sensor detects flow higher than 0.5 GPM, a single LED tick mark on the left side of
the 3-digit 7-Seg. LED will blink to indicate that the unit is working.
Example: tick mark next to the 110°F set temperature display
520 Indoor / 520 Outdoor Service Manual
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