Troubleshooting - Bradford White UCG100H3993N Service Manual

System Observation for Models with Direct Spark Ignition
Water Heater Fault: Water heater does not operate
Display Error Code: Water heater display does not
operate - blank display
Check main power supply to water heater –
fuse, circuit breaker, plug receptacle, line cord or
wiring to water heater.
Check to make sure switch on front of control
panel is in the ON position.
Verify primary voltage at the transformer.
Verify secondary voltage at the control board.
Does water heater display
operate? Increase thermostat
setting if tank is warm.
Y
Display operates-See next page.

Troubleshooting

120 volt potential exposure. Use caution making voltage checks
Use caution not to damage connectors when making voltage
Refer to control board illustration.
Voltage at transformer across black and
white wires should be 110-120 VAC.
Check line cord with volt meter. Replace
line cord if defective.
Refer to control board illustration.
Voltage at connector location J8 across
blue and yellow wires should be 24VAC.
If not, check transformer. Replace
transformer if defective.
Is 24VAC present between
N
RED and BLACK wire pin
connections on the back of
control display?
N
Display operates-See next page.
N
Replace control board.
11
WARNING
to avoid personal injury.
CAUTION
measurements or jumping terminals
Check wires for proper
termination to control display.
Y
Are wire terminations connected
properly to control display?
Y
Check wire
harness for proper
continuity.
Black & Yellow &
White Blue
wires. wires.
Y
Replace
control
board.
N
Make proper wire
terminations.
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