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Merlin IV


Beverage Orders
Post Mix
General Diagnostics

Error/Problem Possible Cause / Test Procedure Corrective Action
Coin acceptance/payout (record all errors on paper)
Coin mechanism will accept coins. No power to board. Check to make sure the LED and the sign lighting are lit. Check fuse and transformer.
Harness from coin mech to board is cut or disconnected. Using a voltmeter, check each wire for continuity and to ground.
Short in coin mechanism. Unplug all connections from the control board except the transformer and coin mech connections. Test acceptance. If it accepts, replug each connection one at a time and test acceptance after each.
Acceptor is dirty or other problem may exist (not tuned). Clean acceptor or contact you local coin mech distributor.
Short in control board. If above procedures do not work, replace control board.
No acceptance or rejects a percentage of good coins. Coin returns lever pressing down on acceptor's coin plunger. Make sure changer is mounted correctly and the coin return lever is in the proper position.
Acceptor is dirty or foreign matter is in the path. Clean acceptor or contact distributor.
Coin changer is improperly tuned (if tunable). Contact manufacturing for tuning.
Defective control board. Replace / test control board.
Always accepts coins but give erratic / no credit. IF NO CREDIT: Defective harness between coin mech and control board ( will have "CC" error). Check harness for cut wires or wrong/bad connections. Test each wire for continuity or test to ground. If found to be defective, replace the harness.
IF ERRATIC OR NO CREDIT: Acceptor or coin mech. Replace coin mech and test.
IF NO CREDIT: Defective control board. Replace control board.
Changer will not pay out coins. Defective harness from coin mech to control board. Test vender's manual coin payout. If vender won't pay out using the CPO mode or during sales, check harness for cuts, bad continuity, or wrong connections. If defective, replace and test.
Defective coin mech. Replace coin mech and test. If it pays out, the coin mech was defective.
Defective control board. If coin mech won't pay out coins manually in the CPO mode or during the Sales Mode and the above procedures ahve failed, replace the control board and test payout both in the CPO mode and during a sale.
Change payout buttons are disabled while door is closed or while in Open-door Mode. Enter the Service Mode or access the Coin Payout Mode ("CPO")
Bill Acceptance
Bill acceptor won't pull bill in. No power to validator. Unplug vender for 10 seconds and replug to see if bill acceptor cycles. If not, check acceptor harnessing or replace the bill acceptor.
Wrong acceptor harness on wires of the harness are in the wrong position. Make sure that the acceptor harnessing is correct for your stlye of acceptor and that it is wired properly.
Acceptance disabled by coin mech (if present), or bad harnessing. Make sure that the coin mech is plugged in (accepts coins) and that the coin tubes have enough coins to enable bill acceptance.
Coin mech is not operative. Make sure that the changer harnessing is correctly connected and has continuity. Repair or replace if necessary.
Replace acceptor and test. If acceptor pull bill in, acceptor was defective. Replace bill acceptor.
Bill acceptor takes a bill but will not establish a credit. Defective acceptor harness (credit not getting from acceptor to control board through the harness). Make sure that the acceptor harnessing is correct for style of acceptor and it is plugged in / wired properly.
Defective acceptor. Repace/test acceptor.
Defective control board. Replace/test control board.
Bill acceptor takes a bill and credits, but credit will not erase. Defective/wrong acceptor interface harness. Refer to bill acceptor service manual or bill acceptor representative.
Defective bill acceptor. Replace acceptor, and test acceptance and erasure of credit.
Defective control board. Replace/test control board for erasure of credit.
Acceptor takes a bill and allows payback fo coins without a selection. Controller configurations not set properly. Access vender configurations mode and check the Forced Vend Attempt setting.
Vending Problems
Multiple vending (not cancelling credit) If multiple vending is from all selections, delivery sensor is not cut or improperly ground. NOTE: if the sensor is not present or is cut (defective), the controller will allow up to two products from each column assigned to be vended begore the column is determined to be sold out. Factory adjustment for the trim pot screw on the controller:
  1. Turn screw clockwise until the light comes on.
  2. Turn screw counterclockwise until the light goes out.
  3. Continue turning counterclockwise 1 full turn.
  4. Vend test on columns 7 and 12, and watch the light on the board. Make sure the only time the light comes on is when a product hits the can chute.
Depth setting not set correctly in "SdEP" mode (may be set to single depth). Enter "SdEP" mode and check the setting to make sure it is correct. Refer to "SdEP" section of this manual. NOTE: "SdEP" is always set by the selection number.
Mechanical error. Check the vend motor to ensure the gearing within it is okay. If not replace the vend motor.
Wrong product vending upon selection. Misload by vender loader. Ensure that all product within each column is the same.
Space-to-Sales not set properly. Look for SiS error. Check or reset space-to-sales.
Miswired motor. Check the wiring at each vend motor, at the bottom of the vender's main door, and at the the motor connection on the control board to ensure the wires are in the correct order.
Miswired selection. Check the wiring from the control board to the selection switches.
No vend upon selection. Dry vend (no refund). Chute sensor too sensitive, or a column is jammed or sold out. Check to see if the delivery chute sensor adjustment LED is constantly on. If so, adjust it back to factory setting. See "Delivery Chute Sensor".
Defective chute sensor. Unplug the sensor's connection from the control board. Watch the LED. If the adjusment LED goes out, replace the defective sensor.
Defective control board. If the adjustment LED stays on after unplugging the sensor from the control board, power it down (pull the fuse), and unplug everything from the control board except the main power lead. Reinsert the fuse. If the adjustment LED immediately lights up, turn the screw counterclockwise to see if the light goes out. If not, replace the control board.
Will vend from some but not all columns (allows refund of second choice). Select button, switch, or harnessing. Check the selection switch. Trace the selection harness back to the control board. Replace if necessary.
Defective vend motor harnessing. Trace the individual wire that runs from the motor connection of the control to the vend motor of the defective column. If the wire is cut or pinched, repair or replace the wire/harness.
Defective control board. Measure the voltage at the vend motor's connection at the control board. Measure it on the individual wire for the motor attempted and the wire itself next to the key (neutral). A selection must be made and "hoLd" displayed on the LED, 24 VDC should be registered. If not, replace the control board.
Complete sold-out condition timer is enabled or "StS" has been cleared. Disable timer control. Check space-to-sales settings; reprogram if necessary.
Door switch not working. Open the vender's main door, and make sure the LED displays the Service Mode. If not, check for voltage (5 VDC) with a voltmeter at the door switch. If not, check for voltage (5 VDC) at the door switch's pinout on the control board. If no voltage is found there, replace the control board.
Display shows "Sold Out" immediately upon pressing selection button of a full column (sold-out condition not clearing). Door switch wiring incorrectly connected or cut/pinched. Check for cuts on the two door switch wires going form the switch to the control board. Also, check for bad connections.
Door Switch check the door switch to see if it is defective. Use a voldmeter to measure for voltage between the COM/NO positions and COM/NC positions.
Control Board Check the control board by checking the voltage across the two pins for the door switch on the board. If no voltage is found, replace the control board.
Vender appears dead; no digital display and no lights. Defective main harness. Secondary power harness to the transformer. Lights defective. Replace main harness. Replace secondary power harness.
No digital display; vender lights are on. Transformer not properly connected or defective. Check transformer connection. Check power with voltmeter from transformer to control board. Replace if necessary.
Defective display or display harness. Check display and display harness. Replace if necessary.
Defective control board. Replace control board.
Vendor scrolls message on display but doesn accept money. Defective changer. Replace.
Defective control board. Replace control board.
Changer out of tune. Refer to distributor.
Vendor accepts money but does not establish credit. Defective changer. replace changer.
Defective control board. Replace control board.
Vendor accepts and credits money but does not vend (does not indicate a sold-out condition). Defective selection switch. Check selection switch. Replace if necessary.
Defective selection switch harness. Check harness. Replace if necessary.
Defective control board. Replace control board.
Flashing 8's across the LED. Chips on control board not seated properly. Seat the chips properly.
Bad LED connection. Scrape the pins on the LED and reinstall harness.
Defective control board. Unplug everything from the control board except the LED and main power. If the 8's remain, replace the control board.
Defective components. If the 8's have disappeared from the previous step, begin plugging in harnesses one at a time. Replace whatever causes the 8's to appear.
Solid 8's across the LED. Defective LED. Replace LED and/or harness.
Defective control board. Replace control board.
"Out of Order" on the LED. Corrupted control board. Press the service mode button. Wait approximately 20 seconds for the board to reset. Reprogram the control board. If the problem reappears or the board cannot be reprogrammed, replace the control board.
Popped Circuit Breaker
  1. Check to see if vendor is on cord and if the cord has shorted out.
  2. Unplug vendor from wall outlet and reset the breaker.
  3. Plug a different electrical device into the outlet to make sure that the outlet works.
  4. Open the door of the vending machine.
  5. Look into the lower left hand corner of the door to find the plug that goes to the compresser and unplug it.
  6. Plug machine back into wall.
  7. Circuit Holds
    1. Run a seperate cord to the compressor.
    2. check for amp draw.(Should not be more than 6 amps)
    3. If it does replace compressor.
  8. Circuit Does Not Hold
    1. There is another plug at the lower left hand corner unplug it
    2. Plug it back into the wall to check circuit
    3. Circuit Works
      1. Short is in the main door.
      2. Inspect Coin Mech, Validator, Board, Transformer, or Light Balast.
      3. Eliminate one out of the system until you find the problem
      4. By removing all of these out of the system and plugging it in if it pops the problem is the wiring hardness.
    4. Circuit Does Not Work
      1. Unplug evaporator fan motor, heater, and cold control.
      2. Plug it back in
      3. If it pops again the main power cord is bad
      4. If it does not pop check the components that you have removed.
      5. Replace the corresponding component.