Bunn-O-Matic AXIOM Series Service Manual
SERVICE & REPAIR MANUAL
BUNN-O-MATIC CORPORATION
POST OFFICE BOX 3227
SPRINGFIELD, ILLINOIS 62708-3227
PHONE: (217) 529-6601 FAX: (217) 529-6644
39132.0000C 12/09 ©2008 Bunn-O-Matic Corporation
BUNN-O-MATIC COMMERCIAL PRODUCT WARRANTY
Bunn-O-Matic Corp. (“BUNN”) warrants equipment manufactured by it as follows:
1) All equipment other than as specified below: 2 years parts and 1 year labor.
2) Electronic circuit and/or control boards: parts and labor for 3 years.
3) Compressors on refrigeration equipment: 5 years parts and 1 year labor.
4) Grinding burrs on coffee grinding equipment to grind coffee to meet original factory screen sieve analysis:
parts and labor for 3 years or 30,000 pounds of coffee, whichever comes first.
These warranty periods run from the date of installation BUNN warrants that the equipment manufactured by
it will be commercially free of defects in material and workmanship existing at the time of manufacture and
appearing within the applicable warranty period. This warranty does not apply to any equipment, component or
part that was not manufactured by BUNN or that, in BUNN’s judgment, has been affected by misuse, neglect,
alteration, improper installation or operation, improper maintenance or repair, damage or casualty. This warranty is
conditioned on the Buyer 1) giving BUNN prompt notice of any claim to be made under this warranty by telephone
at (217) 529-6601 or by writing to Post Office Box 3227, Springfield, Illinois 62708-3227; 2) if requested by
BUNN, shipping the defective equipment prepaid to an authorized BUNN service location; and 3) receiving prior
authorization from BUNN that the defective equipment is under warranty.
THE FOREGOING WARRANTY IS EXCLUSIVE AND IS IN LIEU OF ANY OTHER WARRANTY, WRITTEN OR
ORAL, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF EITHER
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. The agents, dealers or employees of BUNN
are not authorized to make modifications to this warranty or to make additional warranties that are binding on
BUNN. Accordingly, statements by such individuals, whether oral or written, do not constitute warranties and
should not be relied upon.
If BUNN determines in its sole discretion that the equipment does not conform to the warranty, BUNN, at its
exclusive option while the equipment is under warranty, shall either 1) provide at no charge replacement parts
and/or labor (during the applicable parts and labor warranty periods specified above) to repair the defective
components, provided that this repair is done by a BUNN Authorized Service Representative; or 2) shall replace
the equipment or refund the purchase price for the equipment.
THE BUYER’S REMEDY AGAINST BUNN FOR THE BREACH OF ANY OBLIGATION ARISING OUT OF THE SALE OF
THIS EQUIPMENT, WHETHER DERIVED FROM WARRANTY OR OTHERWISE, SHALL BE LIMITED, AT BUNN’S
SOLE OPTION AS SPECIFIED HEREIN, TO REPAIR, REPLACEMENT OR REFUND.
In no event shall BUNN be liable for any other damage or loss, including, but not limited to, lost profits, lost sales,
loss of use of equipment, claims of Buyer’s customers, cost of capital, cost of down time, cost of substitute
equipment, facilities or services, or any other special, incidental or consequential damages.
AutoPOD, AXIOM, BrewLOGIC, BrewMETER, Brew Better Not Bitter, BrewWISE, BrewWIZARD, BUNN Espress,
BUNN Family Gourmet, BUNN Gourmet, BUNN Pour-O-Matic, BUNN, BUNN with the stylized red line, BUNNlink,
Bunn-OMatic, Bunn-O-Matic, BUNNserve, BUNNSERVE with the stylized wrench design, Cool Froth, DBC, Dr.
Brew stylized Dr. design, Dual, Easy Pour, EasyClear, EasyGard, FlavorGard, Gourmet Ice, Gourmet Juice, High
Intensity, iMIX, Infusion Series, Intellisteam, My Café, PowerLogic, Quality Beverage Equipment Worldwide,
Safety-Fresh, savemycoffee.com, Scale-Pro, Silver Series, Single, Smart Funnel, Smart Hopper, SmartWAVE,
Soft Heat, SplashGard, The Mark of Quality in Beverage Equipment Worldwide, ThermoFresh, 392, Beverage Bar
Creator, Beverage Profit Calculator, BUNNSource, Coffee At Its Best, Digital Brewer Control, Nothing Brews Like
a BUNN, Pouring Profits, Respect Earth, Respect Earth with the stylized leaf and coffee cherry design, Signature
Series, Tea At Its Best, The Horizontal Red Line, Titan, Ultra are either trademarks or registered trademarks of
Bunn-O-Matic Corporation.
Page 2
39132 110909
INTRODUCTION
This equipment will brew a half-gallon batch of coffee into an awaiting dispenser. It can be easily configured for
120V 15 amp, 120/208V 20 amp or 120/240V 20 amp. The brewer may have a hot water faucet for allied beverage use.
It is only for indoor use on a sturdy counter or shelf.
CONTENTS
Troubleshooting ..................................................................................................4
Diagnostics .........................................................................................................9
Technician Programming Reminders ................................................................10
Access ..............................................................................................................11
Control Board ....................................................................................................12
Face Plate ..........................................................................................................13
Membrane Switch .............................................................................................13
Brew Valve ........................................................................................................14
Optional Brew Valve ..........................................................................................15
Level Probes .....................................................................................................16
Early Refill Valve ...............................................................................................17
Later Refill Valve ...............................................................................................18
Tank Heaters .....................................................................................................20
Limit Thermostat ...............................................................................................21
Thermal Cut Off .................................................................................................21
Blanket Warmer ................................................................................................22
Temperature Probe............................................................................................23
Warmer Elements..............................................................................................24
Voltage Selector Switch ....................................................................................25
Power Switch ....................................................................................................26
Programming Level 3 ........................................................................................27
Programming Level 4 ........................................................................................29
Wiring Diagrams .............................................................................................. 30
Schematics .......................................................................................................34
Page 3
39132 062309
TROUBLESHOOTING
A troubleshooting guide is provided to suggest probable causes and remedies for the most likely problems
encountered. If the problem remains after exhausting the troubleshooting steps, contact the Bunn-O-Matic
Technical Service Department.
• Inspection,testing,andrepairofelectricalequipmentshouldbeperformedonlybyqualiedservicepersonnel.
• Allelectroniccomponentshaveaclinevoltageandsomehavelowvoltagedcpotentialontheirterminals.
Shorting of terminals or the application of external voltages may result in board failure.
• Intermittentoperationofelectroniccircuitboardsisunlikely.Boardfailurewillnormallybepermanent.If
an intermittent condition is encountered, the cause will likely be a switch contact or a loose connection at a
terminal or crimp.
• Solenoidremovalrequiresinterruptingthewatersupplytothevalve.Damagemayresultifsolenoidsare
energized for more than ten minutes without a supply of water.
• Theuseoftwowrenchesisrecommendedwheneverplumbingttingsaretightenedorloosened.Thiswill
help to avoid twists and kinks in the tubing.
• Makecertainthatallplumbingconnectionsaresealedandelectricalconnectionstightandisolated.
• Thisbrewerisheatedatalltimes.Keepawayfromcombustibles.
WARNING
• Exercise extreme caution when servicing electrical equipment.
• Unplug the brewer when servicing, except when electrical tests are specied.
• Follow recommended service procedures.
• Replace all protective shields or safety notices.
Before assuming a faulty control board, check for the following:
Control Boards
1. Make sure ribbon cable is properly attached to the control board (ALL PINS INSERTED INTO PLUG).
2. Make sure there is a nylon insulating washer under each screw head that holds the control board to the
plastic front end cap. This is important for proper operation.
3. Make sure, before servicing brewer that voltage is present at control board.
4. Press any warmer switch (if equipped) or observe if any indicator lights are glowing on the control panel.
If so, proceed with testing. If not, check for voltage across pins 1 & 2 of the ten pin J1 connector (black and
white wires). If voltage is present, replace the control board. If voltage is not present, check wiring and voltage
across terminal block (black and white on 120 & 120/240 models, or black and red on A models). Correct the
problem and retest before proceeding with testing.
Page 4
39132 062309
TROUBLESHOOTING (cont.)
REFILL CIRCUIT
PROBABLE CAUSE REMEDYPROBLEM
Will not refill
Refill does not shut off
Power "ON"
1. Power off to brewer
2. Water shut off
3. Error Message
4.ON/OFF Switch
(If equipped)
5. Lime build up on Probe(s)
6. Refill Valve or Control Board
1. Lime build up on probe
Press OFF/ON switch on control
panel to determine if power is ON.
Make sure water is ON.
Brewer has shut down due to malfunction (See Diagnostic Section in
this manual).
Make sure ON/OFF Switch is "ON"
and indicator is lit.
Remove the Level Probe(s) and
check for lime deposit on tip. Clean
and reinstall.
Refer to page 19
Remove Level Probe and check
for lime deposits on tip. Clean and
reinstall.
Refill does not shut off
Power "OFF"
2. Water Level Sensing System
3. Refill valve or control board
1. Refill valve
Replace control board
Check valve. Page 19
Clean or replace valve as needed.
Page 19
Page 5
39132 080409
TROUBLESHOOTING (cont.)
HEATING CIRCUIT
PROBLEM
Water does not heat to proper
temperature
IMPORTANT: Make sure no temperature tests are taken before
the display reads ready. Tank temperature must be stabilized before
readings are taken.
PROBABLE CAUSE REMEDY
1. Display's error message
Brewer has shut down due to malfunction. See Diagnostics.
2. Water not touching main (short)
level probe
Remove level probe and grommet.
Look into hole on tank lid. Water
must be within approximately one
inch from top of tank.
3. Water Level Probe Sensing
System
Check refill circuit. Heaters will not
turn on if water is not grounding
level probe.
4. Temperature Probe
5. Limit Thermostat or TCO
6. Tank Heater
Check/replace
Check/replace
Check/replace
Spitting or excessive steaming
(cont.)
Brewer is making unusual noises
1. Lime build up on temperature
probe, tank or tank heater
2. Temperature Probe
3. Control Board
1. Plumbing lines
2. Water supply
3. Lime build up
Inspect probe and tank assembly
for excessive lime deposits. Delime
as required.
Check/replace
Check/replace
Plumbing lines should not rest on
the counter top.
The brewer must be connected to
a cold water supply.
Remove the tank lid and clean inside of tank with a deliming agent,
if necessary.
Page 6
39132 041708
TROUBLESHOOTING (cont.)
BREWING CIRCUIT
PROBLEM
Brew cycle will not start
PROBABLE CAUSE REMEDY
1. Display's error message
Brewer has shut down due to malfunction. See Diagnostics.
2. No water
Water lines and valves to the brewer
must be open.
3. No power or incorrect voltage to
the brewer
4. ON/OFF switch not in the "ON"
Check for voltage across the terminals at the terminal block.
The indicator lamp must be lit
position
5. Low water temperature (Brew
lockout is enabled)
Allow brewer to heat until ready, or
disable the brew lockout feature.
Water must be in contact with refill
6. Water not touching refill probe
probe before brew cycle will start.
inside tank
Check/replace
7. Membrane Switch
Check/replace
Consistently low beverage level in
the dispenser or beverage overflows
dispenser
Brew cycle starts, then aborts and
returns to Main screen after 20
seconds (SB 153)
8. Dispense valve
9. Control board
1. Brew volume
NOTE: Volume adjustments must be
made with sprayhead installed.
2. Lime build up
3. Dispense Valve
1. Level probes shorted
2. On pourover models, the operator poured in water and pressed the
start button
Check/replace
Inspect the dispense valve and
sprayhead for excessive lime deposits. Delime as required.
Remove dispense valve and clear
any obstructions. Rebuild or replace
valve if necessary. (See page 24)
Check/replace
Delime as required.
Ensure mylar shield(s) are installed
on top cover
Instruct operator to use one procedure but not both
Page 7
39132 061809
TROUBLESHOOTING (cont.)
BREWING CIRCUIT (cont.)
PROBLEM PROBABLE CAUSE REMEDY
Dripping from sprayhead
Weak beverage
1. Lime build up
2. Dispense valve
1. Sprayhead
2. Water temperature
3. Filter type
Inspect the tank assembly for
excessive lime deposits. Delime
as required.
Check/replace
A clean sprayhead must be used
for proper extraction.
Place an empty brew funnel
on an empty decanter beneath
the sprayhead. Initiate brew
cycle and check the water temperature immediately below the
sprayhead with a thermometer.
The reading must not be less
than 195°F (91°C). Adjust the
temperature setting to increase
the water temperature. Refer to
Initial Set-up instructions.
BUNN® paper filters must be
used for proper extraction.
Dry coffee grounds remain in
the funnel
Low beverage serving temperature
4. Coffee grind
5. Funnel loading
1. Sprayhead
2. Funnel loading
1. Warmer
2. Thermal server/airpot not
preheated before brew cycle
A fine drip or grind must be used
for proper extraction.
The BUNN® paper filter must
be centered in the funnel and
the bed of grounds leveled by
shaking gently.
Make sure sprayhead is present and holes are clear and
unobstructed.
The BUNN® paper filter must
be centered in the funnel and
the bed of grounds leveled by
shaking gently.
Check/replace
Preheat server
Page 8
39132 041708
DIAGNOSTICS
MESSAGE
"CHECKSPRAYHEADFORLIME"-
"CHECKFITTINGSFORLIME"
"WARNING INACCURATE FLOW"
- "TOO MUCH LIME PLEASE REPAIR"
"WARNING VERY LOW FLOW" -
"PLEASE REPAIR"
Temperature Too Low
PROBABLE CAUSE REMEDY
1. Lime buildup in sprayhead
2. Lime buildup in brew valve
3. Lime buildup in brew tank
1. Lime buildup in sprayhead
2. Lime buildup in brew valve
3. Lime buildup in brew tank
1. Lime buildup in sprayhead
2. Lime buildup in brew valve
3. Lime buildup in brew tank
1. Water temperature in the tank
does not meet the ready tempera-
Clean sprayhead
Clean valve
Clean tank
Clean sprayhead
Clean valve
Clean tank
Clean sprayhead
Clean valve
Clean tank
A) Wait for the brewer to heat to
the proper temperature.
ture.
B) Disable the BREW LOCKOUT
function. Refer to programming
section for procedure.
Heating Time Too Long
Fill Time Too Long
Temp Sensor Out Of Range, Check
For Bad Connections
Temp Sensor Out Of Range, Check
Wire For Shorts
1. Tank Heater failure.
2. Control Board/Thermistor failure
1. Water shut off to brewer
2. Supply line too small or obstructed
3. Inlet Solenoid failure
4. Control Board Failure
5. ON/OFF switch is OFF
1. Temperature Sensor Probe
open
1. Temperature Sensor Probe
wire(s) shorted
Page 9
Replace or repair as needed
Replace or repair as needed
Check water supply shut-off
Replace or repair as needed
Replace or repair as needed
Replace or repair as needed
Turn switch ON
Replace or repair as needed
Replace or repair as needed
39132 041708
TECHNICIAN PROGRAMMING REMINDERS
REVERSE FORWARD
REVERSE FORWARD
AXIOM
VERSION ##.##
VIEW ASSET/SERIAL # ENTER PROGRAMMING
ACCESSING PROGRAM MODES
Press and hold the right hidden switch. The longer you press it, the higher the level you can access. EXAMPLE:
Pressing for a couple seconds enters Level 1. Continuing to press for approximately 5 seconds will access Level
2. Continue pressing for approximately 15 seconds to access Level 3. During program modes, use the right hid-
den switch to advance forward through screens. Use left hidden switch to step backwards through screens.
VIEWING ASSET AND SERIAL NUMBERS
Press left hidden switch to view Asset number. Press and release to view serial number. Press and release again
to view the installed software version.
FACTORY BLOWOUT MODE
When in the main screen, DO NOT press both left and right hidden switches at the same time. The display will
read"FACTORYBLOWOUT""ON/OFF". WARNING: NEVER activate this mode. It will open the brew and refill
valves simultaneously. THIS IS FOR FACTORY USE ONLY! If you accidentally enter this screen, exit out of it
by pressing the "ENABLE BREW ON/OFF" switch.
PROGRAMMING LOCKOUT SWITCH
(Mounted on main control board)
This switch can be set to prevent access
to Level 2. Turn "OFF" the switch to access
Technician (Level 2). Once all the correct brew
settings are programmed, the Technician can
set the switch to the "ON" position to prohibit
anyone from changing the settings. With the
switch in the "ON" position, only Level 1 can
be accessed by store personnel. Technicians
can access Level 1 with the switch in either
position. To enter Levels 2, 3, & 4, press and
hold right hidden switch.
Page 10
39132 062309
COMPONENT ACCESS
This section provides procedures for testing and
replacing various major components used in this
brewer should service become necessary. Refer to
Troubleshooting for assistance in determining the
cause of any problem.
WARNING - Inspection, testing, and repair of electrical equipment should be performed only by qualified
service personnel. The brewer should be unplugged
when servicing, except when electrical tests are required and the test procedure specifically states to
plug in the brewer.
WARNING - Disconnect the brewer from the power
source before the removal of any panel or the replacement of any component.
All components are accessible by the removal of
the top cover or warmer housing, front access panel
and warmer plate(s).
Refer to wiring diagrams at the back of this manual
when reconnecting wires.
FIG. 11-1 COMPONENT ACCESS
Page 11
FIG. 11-2 COMPONENT ACCESS
39132 062309
CONTROL BOARD
FIG. 12-1 CONTROL BOARD
Location:
The Control Board is located inside the top cover
behind the front face plate.
5. Remove the two screws and two nylon washers
securing the control board to the front face plate.
6. Tilt the control board inward to clear the display
section.
7. Place the bottom edge of the new control board
in the two cradles, tilt the board forward, and secure
with the two screws and nylon washers to the front
face plate.
NOTE: The nylon washers must be installed under
the heads of the two screws to prevent a possible
shorting of the control board circuits.
8. Re-install wires & connectors.
BEFORE REPLACEMENT:
If a triac or MOV is visibly burned, it was most likely
caused by an external sourcs such as a shorted wire
or damaged solenoid coil. Use the triac map below
to trace the circuit in question, and repair/replace the
component before replacing control board.
Test Procedures:
The test procedures for the control board will vary
depending upon the problems experienced by the
brewer. Refer to the Troubleshooting section which
is divided into three sections, Refill Circuit, Heating
Circuit, and Brewing Circuit.
Check for Power to board:
1. Insert one meter lead in J1-pin 1 and the other
lead in J1-pin 2.
2. With the power connected to brewer, the voltage
reading to the board should be the line voltage rated
for that model.
If no voltage is present, check wiring to the board.
If voltage is present, and brewer does not power
on, replace board.
Removal and Replacement:
1. Disconnect brewer from power source.
2. Disconnect the wires from the relay on the control
board.
3. Disconnect the 10-pin connector (main harness)
and the 3-pin connector (level probe harness) from
the control board.
4. Disconnect the 10-pin connector (ribbon cable)
from the control board.
FIG. 12-2 TRIACS
Triac Map:
TH1 Warmer
TH2/MOV-1 Brew solenoid
TH3 Warmers
TH4/MOV-2 Refill solenoid
TH5 Main warmer
TH5
TH4
MOV2MOV1
TH3
TH2
TH1
@ J1-7
@ J1-10
@ J1-4&8
@ J1-5
@ J1-6
Page 12
39132 041708
FACEPLATE REMOVAL
Faceplate Removal and Replacement:
1. Disconnect brewer from power source.
2. Disconnect the wires from the relay on the control
board.
3. Disconnect the 10-pin connector (main harness)
and the 3-pin connector (level probe harness) from
the control board.
4. Disconnect the 10-pin connector (ribbon cable)
from the control board.
5. Drain tank and disconnect/remove faucet.
6. Remove the 3 nuts and 1 standoff from back side
of faceplate assembly.
7. Remove faceplate and control board as an assembly
out the front opening.
8. Remove the two screws and two nylon washers
securing the control board to the front face plate.
9. Place the bottom edge of the new control board in
the two cradles and secure with the two screws and
nylon washers to the front face plate.
NOTE: The nylon washers must be installed under
the heads of the two screws to prevent a possible
shorting of the control board circuits.
10. Re-install faucet assembly (if equipped).
11. Re-install faceplate/board assembly.
12. Re-install wires & connectors.
FIG. 13-1 FACEPLATE REMOVAL
Page 13
39132 061809
Helpful
Hint
MEMBRANE SWITCH
FIG. 14-1 MEMBRANE SWITCH
you can test it with an ohmmeter or continuity tester.
Refer to the schematic to trace the appropriate pins.
NOTE: 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.
Removal and Replacement:
1. Disconnect the ribbon cable from 10-pin connector
on the control board.
2. Gently peel the membrane switch from the front
face plate assembly.
4 Remove any adhesive that remains on the front
face plate.
5. 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.
6. 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.
Location:
The Membrane Switch is located on the front face
plate.
Test Procedures:
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,
Wrap a thin paper clip around each meter lead
and extend past the tip by ¼" - ½".Youmay
need to sand off the clear coating on some clips!
FIG. 14-2 MEMBRANE SWITCH CONTINUITY
Page 14
39132 100609
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