Mechanical Or Refrigeration Failure - Bunn JDF Silver Series Technical Training Manual

Mechanical or Refrigeration Failure

If a repair to the refrigeration system is needed it is required that a certified refrigerant technician handles the repair.
When troubleshooting and repairing any unit with a refrigeration system, the servicing technician needs to check all
possible mechanical failures before contacting a certified refrigerant technician.
The JDF 2S and 4S has one symptom, bath not freezing, where it could be a failure with the refrigeration system.
The bath not freezing is a major fault condition that will need to be determined during troubleshooting if a certified
refrigerant technician needs to be involved on repairing the dispenser. It is up to the servicing technician to determine
if the symptom is caused by a component failure or low refrigerant charge.
Troubleshooting Guide
Bath Frozen
Bath water recirculation problem or control circuit failure. The dispenser will need to be unplugged for 48 hours to
allow complete thaw of bath tank.
Step 1: After thaw of frozen bath, refrigeration switch turned on, determine if recirculating pump is moving water by
simply lifting braided water return hose along side right rear of pump motor. The pump does have by-pass holes in
bottom of pump housing for increased water agitation in bath tank.
Yes: Recirculating pump is okay. Go to the next step and begin the process of troubleshooting the control
circuits.
No: Determine pump motor is getting its 120VAC supply when the refrigeration switch is turned on.
120VAC present – Replace recirculating pump assembly.
120VAC not present – Defective switch or loose wire connection in circuit.
Step 2: Bath thermistor can be out of range and cause frozen bath. Thermistor frozen in ice must read 31 K ohms or
greater and will be approximately around 2.0VDC reading. Determine if the ohms value is in relation with real time
temperature. Ohms/Temp chart is available and with notes under Refrigeration and Cabinet Cooling section.
Yes: Go to the next step.
No: Replace bath thermistor.
Step 3: Compressor K1 relay normally open contacts could be welded together keeping compressor running 24/7,
frozen bath. Unplug unit and check normally open contacts for continuity.
Yes: Replace compressor K1 relay.
No: Go to the next step.
Step 4: Circuit failure within the main control board can cause frozen bath. Upon initial or every power up, control
board has a built in 6 minute time delay before activating 120VAC output to K1 relay coil to close the normally open
K1 contacts to turn on the compressor.
Install voltmeter across K1 relay coil and plug in unit, monitor 6 minute delay before 120VAC is present across K1
relay coil. Ultimately if steps 1 thru 3 check out good you will be replacing main control board as a last result step
before step 5.
Step 5: You can have the same symptoms of a frozen bath if the product coil has shifted in the bath tank and is too
close to the ice block which freezes the water in the product coil.
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