A.O. Smith BTH 120-250(A) - Manual (Page 16)

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NO LOW VOLTAGE (Figure 20)
24V AC LED Off
NO LOW VOLTAGE, 24V AC LED Off
FIGURE 20
TEMPERATURE PROBE FAULT (Figure 21)
Water Temp LED Flashing
TEMPERATURE PROBE FAULT, Water Temp LED Flashing
FIGURE 21
This condition accommodates multiple failure modes. To more accurately
determine the cause of failure, press the pushbutton on the display board.
FAULT CONDITIONS
The controller is set up to provide additional status indicators under Fault
Conditons. The following figures are possible Fault Conditions.
NO INCOMING LINE VOLTAGE (Figure 19) Line LED Off
Possible Cause Remedy
1. Burner ground wire broken 1. Check wire and connection
or corroded at burner
2. Connectors unplugged 2. Check connections
3. Igniter broken 3. Replace igniter
4. Flame probe faulty 4. Replace flame probe
5. Gas shut off 5. Turn on gas supply
6. Clogged gas valve 6. Replace gas valve
7. Faulty gas valve 7. Replace gas valve
8. Defective control 8. Replace control
9. Burner improperly adjusted 9. Adjust burner
10. Dirty burner 10. Clean burner
GAS VALVE LED FLASHING
This condition results from a failure to establish burner ignition after three
successive trials. In such cases:
1. Investigate the possible cause and remedy any observations.
2. Momentarily depress the button on the display panel to reset the lockout
condition.
3. Confirm proper appliance operation.
NO INCOMING LINE VOLTAGE, Line LED Off
FIGURE 19
Possible Cause Remedy
1. No Input Power 1. Apply Power
2. Wiring Disconnected 2. Check all wiring
3. One or more wiring receptacles 3. Reconnect plugs on control,
disconnected from control confirm all are fully seated
4. LED burned out 4. Ignore or replace control
Possible Cause Remedy
1.Blower 24 VAC Fuse 1. Replace 24 VAC 3a Fuse
(Littlefuse 257003 automotive fuse).
2.Defective Transformer 2. Replace Transformer
3.LED burned out 3. Ignore or replace control