A.O. Smith HW 300 Instruction Manual page 37

The following procedures are provided as a general guide.
Any module should be replaced if it does not perform properly on
checkout or troubleshooting.
In addition, replace any module if it is wet or looks like it has ever
been wet.
LED STATUS AND TROUBLESHOOTING
The control has two LEDs; one for flame sensing and one for
system status:
FIGURE 22. LOCATION OF LED'S
• Flame LED (Yellow)
Indicates flame presence and strength. Refer to Table 18.
• Status LED (Green)
Indicates system operation status and error conditions. Refer
to Table 19 and Table 20 on Pages 38 and 39 for status
specific to each model.
TABLE 18. YELLOW LED FLAME CODES
YELLOW LED
FLASH CODE
A
Heartbeat Normal Flame Signal
Weak Flame Signal-
System will operate
reliably but flame
signal is less than
desired.
2
NOTE: This indication
may flash temporarily
during or shortly
after lightoff on some
applications.
Marginal Flame Signal
(less than 1.1µA)-
System may not
operate reliably over
time.
Service call
1
recommended.
NOTE: This indication
may flash temporarily
during or shortly
after lightoff on some
applications.
No Flame or Flame
Signal below minimum
OFF
threshold for system
operation.
Flash Code Descriptions:
A
• Heartbeat: Constant 1/2 second bright 1/2 second dim
cycles.
• The flash code number signifies that the LED flashes X
times at 2Hz, remains off for two seconds, and then repeats
the sequence.
37
RECOMMENDED
INDICATES
SERVICE ACTION
not applicable
Perform routine
maintenance to
assure optimum
flame signal.
Check gas supply,
pilot burner, flame
sense wiring,
contamination
of flame sensor,
burner ground
connection.
not applicable