Bunn FMD-4 User Guide

Tank Heater Relay Control Circuitry (Control Board #2)

(120V dispensers only):

1. Disconnect the dispenser from the power

source.

2. Disconnect the six pin connector from J3 of control

board #2.

3. Check the voltage across pins 5 & 6 of the six pin

connector on the wiring harness with a voltmeter.

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

diagram and check the dispenser wiring harness.

5. Reconnect the six-pin connector of the wiring

harness to J3 of control board #2.

6. Disconnect the four-pin connector from J4 of

control board #2.

7. Check the voltage across pins 1 & 4 of the four-pin

connector on the wiring harness with a voltmeter.

The indication must be 120 volts ac.

8. Disconnect the dispenser from the power

source.

If voltage is present as described, proceed to step 9.

If voltage is not present as described, refer to the wiring

diagram and check the dispenser wiring harness.

9. Reconnect the four-pin connector of the wiring

harness to J4 of control board #2.

10. Check the voltage across the coil terminals of the

tank heater relay with a voltmeter. Connect the

dispenser to the power source. The indication

must be 0 volts ac.

If voltage is absent as described, proceed to step

11.

If voltage is present, replace the control circuit board

#2.

11. Place containers below any three dispenser

nozzles.

12. Simultaneously initiate dispenses at each of the

selected dispense stations while monitoring the

voltage across the coil terminals of the tank heater

relay. The indication must be 120V ac.

If voltage is present as described, the control board

#2 is functioning correctly.

If voltage is not present as described, replace the

control circuit board #2.

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.

NOTE: J4 is not connected on Control Board #2 on

120/208 - 240V dispensers.

J4 J3

FIG. 12 CONTROL BOARD CONNECTORS

P2637

J1 J2

J4 J3

CONTROL BOARD #1

CONTROL BOARD #2

35135 111103