Troubleshooting - Bradford White EF120T4003N3 Service Manual

System Observation for 120T400/500 Models with Direct Spark Ignition
Water Heater Fault: Water heater does NOT operate.
Display Error Code: Water heater digital display does
NOT operate - blank display.
Check main power supply to water heater.
Check fuse, circuit breaker, plug receptacle, line
cord, and wiring to water heater.
Check to make sure switch on front of control
board is in the ON position.
Verify primary voltage at the transformer.
Verify secondary voltage at the control
board.
Does the water heater digital
display operate? Increase
thermostat setting if tank is warm.
N
Is 24-28 VAC present
between red and black wire
pin connections on the back
of control board?
N
Check wires for proper
termination to control board. Are
wire terminations connected
properly to digital display?
Y
Check wire
Y
harness for proper
continuity.

Troubleshooting

Refer to control board illustration.
Voltage at transformer across black and
white wires should be 110-120 VAC.
Verify 120V from the power switch.
Refer to control board illustration.
Voltage at connector location J8 across
blue and yellow wires should be 24-28
VAC. If not, check transformer. Replace
transformer if defective.
Digital display
operates– see
next page.
Y
Replace digital display.
Replace control board.
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
Use caution to NOT damage connectors when
making voltage measurements or jumping terminals.
Black & White
wires
120T Control Board Schematic
11
WARNING
CAUTION
Yellow & Blue
wires
11