Bunn FMD-3 Operating & Service Manual page 20

SERVICE (cont.)
CONTROL BOARD (cont.)
17. Gently pull the liquid level probe out of the tank lid
and inspect for corrosion. Replace it if necessary.
18. Place the probe so that neither end is in contact
with any metal surface of the dispenser.
19. With a voltmeter, check the voltage across the
terminals of the inlet solenoid valve. Connect the
dispenser to the power source. The indication must
be:
a) 120 volts ac for two wire 120 volt models, three
wire 120/208 volt and 120/240 volt models,
b) 240 volts ac for two wire 240 volt models,
c) 230 volts ac for two wire 230 volt models, after
a delay of approximately 10 seconds.
20. Move the probe's flat end to the dispenser housing.
The indication must be 0.
21. Move the probe's flat end away from the housing.
The indication must, again, be:
a) 120 volts ac for two wire 120 volt models, three
wire 120/208 volt and 120/240 volt models,
b) 240 volts ac for two wire 240 volt models,
c) 230 volts ac for two wire 230 volt models, after
a delay of approximately 5 seconds.
22. Disconnect the dispenser from the power source.
If the voltage is present as described, re-install the
probe. The liquid level control circuitry is operating
properly.
If the voltage is not present as described, check the pink
probe wire and green tank wire for continuity.
Hopper Motor Control Circuitry:
1. Disconnect the dispenser from the power source.
2. Disconnect the six pin connector from J3 of the
control board.
3. With a voltmeter, check the voltage across pins 5 &
6 of the six pin connector on the wiring harness.
Connect the dispenser to the power source. The
indication must be 24 volts ac.
4. Disconnect the dispenser from the power source.
If voltage is present as described, proceed to step 5.
If voltage is not present as described, refer to the Wiring
Diagrams and check the dispenser wiring harness.
5. Reconnect the six pin connector of the wiring har-
ness to J3 of the control board.
6. Check that the rinse/run switch is in the run posi-
tion.
7. With a voltmeter, check the voltage across the red
(+) terminal and the black (-) terminal of the auger
motor. Connect the dispenser to the power source.
Press and hold the appropriate dispense switch.
After a delay of about .6 seconds, the indication
must be between +4.0 and +24.5 volts dc.
If the voltage is present as described, the hopper motor
control circuitry is operating properly.
If the voltage is not present as described, replace the
control circuit board.
Removal and Replacement:
1. Disconnect the three plugs on the main wiring har-
ness from the connectors on the control board.
2. Remove the four #6-32 keps nuts securing the
control board to the component bracket.
3. Remove control board and discard.
4. Install new control board on the component bracket
using four #6-32 keps nuts.
5. Reconnect the three plugs on the main harness to
the connectors on the control board.
J2 J3
J 1
FIG. 8 CONTROL BOARD CONNECTORS
20
J 2
J 3
J 4
J1 J4
P1640
29170 091598