BUNN - AXIOM SERIES _ BREWER _ Service Help _ Contn: 2 of 5

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MEMBRANE SWITCH

• Can test it with an ohmmeter or continuity tester.
• Pin 1 is the static shield & will not provide a reading to the other pins. There are two commons in this circuit, pins 9 & 10.
• Disconnect brewer from power source before disconnecting ribbon cable from control board.
• Disconnect the ribbon cable from 10-pin connector on the control board.
• Gently peel the membrane switch from the front face plate assembly.
• Remove any adhesive that remains on the front face plate.
• Remove the adhesive backing from the new membrane switch. Insert the ribbon cable through the slot in the front face plate and apply the membrane switch to the front face plate.
• Connect the ribbon cable to the 10-pin connector on the control board making sure every pin on the control board is inserted into the ribbon cable connector.
• The Membrane Switch is located on the front face plate.

TEST

There are two methods for testing the membrane switch.

• The easiest method is to use the built in test mode.
• Refer to the Programing Section for Service Tools/Test Switches.
•  If for some reason you can't get into the program modes, or brewer won't power up observed, brew valve is defective.
•  Replace valve and test again to verify repair.
• If voltage is not present as described, refer to Wiring Diagrams and check the brewer wiring harness.
• Also check the control board and switch for proper operation.

BREW VALVE

• The brew valve is located inside the top cover behind the front face plate.
• Disconnect the brewer from the power source.
• Disconnect wires from the valve.
• Drain enough water from the tank so the water level is below the outlet.
• Remove hoses from the valve.
• Remove the two * 8-32 nuts securing the valve to the sprayhead panel.
• Install new valve using the two * 8-32 nuts.
• Reconnect hoses to the valve and secure in place with clamps.

TEST

• Be sure brew funnel & server are in place before activating valve.
• Check the valve for coil action. Turn on the valve with the test mode. Listen carefully in the vicinity of the brew valve for a click as the coil pulls the plunger in.  If no sound is heard as described, proceed to *4.
• If the sound is heard as described, there may be a blockage in the valve , hose, tank, or sprayhead.
•  Disconnect the brewer from the power source.  Remove the valve and inspect for blockage, and de-lime all related areas.

 * 4 : Connect the voltmeter leads to the coil terminals.

• Turn on the valve with the test mode.
• Due to the internally rectified coil, the indication will be 120VAC all the time. Set the meter to DC volts. The indication should be 170VDC when activated. If the polarity of meter leads are reversed, reading will indicate -170VDC. (Double these readings for 240 volt coils).

• If voltage is present as described, but no coil action is observed, brew valve is defective.
• Replace valve and test again to verify repair.
• If voltage is not present as described, the brewer wiring harness.
• Also check the control board and switch for proper operation

REMOVAL AND REPLACEMENT

• Disconnect the brewer from the power source.
• Disconnect wires from the valve.
• Drain enough water from the tank so the water level is below the outlet.
• Remove sprayhead and hose from the valve.
• Remove the nut securing the valve to the sprayhead panel.
• Install new valve using the nut.
• Reinstall sprayhead and hose to the valve and secure in place with clamps

OPTIONAL BREW VALVE [ON SELECT MODELS]

LEVEL PROBE SYSTEM

• The level probes are located inside the tank lid.

OPERATION

• The level probes sense the water level in the tank by the conductive minerals in the water grounding out the very low AC voltage applied to the probes. The circuit monitors the time it takes the water to drop the distance from the short probe to the long probe.  Proper "initial set up", and keeping mineral build up off the probes/grommets, is required for this system to operate properly. A brew abort feature is "built in".  In the event that the drop in water level from the short probe to the long probe takes too long, the brew cycle will abort and return to the main screen. This could be caused by: Mineral build up on probes/grommets (very hard water); probes shorting to top cover (verify the mylar shield(s) are installed; plugged outlet (ie:sprayhead limed up); incorrect operator use with the pour over model (ie: pour in water and pressing "start" button).

TEST PROCEEDINGS

• Enter programming level 2, scroll to "Refi ll". NOTE: This screen only reads the long probe (blue wire) and is used for setting the refill Conductance threshold.
• Alternate: Scroll to "Service Tools".  Then scroll to "LP1 & LP2". LP1 = short probe, LP2 = long probe.
• A high reading (approximately 255) indicates water is not touching, or not conductive enough to ground the circuit. A low reading (0-2) indicates the probe is grounded.

REMOVAL AND REPLACEMENT

• Disconnect the brewer from the power source and allow tank to cool.
• Remove nut, wire, and washers from probe.
• Pull probe straight up from grommet.
• When reinstalling, ensure long probe is connected to the blue wire, and short probe is connected to the brown wire.
• Heavy mineral build up on probes could indicate that the tank, lid, and grommets may need to be de limed as well.

Level Probes

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