A.O. Smith 240 T-H3J Service Manual page 41

10-16. Overheat cut off fuse
Part#
Function
Failure events
Effects on the water heater
if the overheat cutoff fuse
fails
Error codes when the
overheat cutoff fuse fails
Diagnostic
Color / Number of wires
240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
communication between the computer board and gas valves will sever,
shutting down the water heater instantly. The "111" or "121" error code
will display.
heater.
2. Gas valves will not operate.
111
Blue-Blue
41
Page
CONFIDENTIAL
Unit Part#
121
Checkpoint
5-1/32" (128 mm)
Ver. 1.00
#413
C2