User Guide & Service Manual
USER GUIDE
 Troubleshooting - Extended 3
u-line.com
SAFETY • INSTALLATION & INTEGRATION • OPERATING INSTRUCTIONS • MAINTENANCE • SERVICE
MAIN CONTROL
The main control board is very robust and is rarely the 
cause of system issues. It is important to fully diagnose 
the board for any suspected failures before attempting to 
remove the board for replacement or service. Follow the 
guidelines below to fully test and diagnose the main 
control.
Power Fault
If the unit does not (or seems to not) power on, follow the 
flow chart below to help diagnose the issue. Before 
beginning it is important to first verify the unit is not 
simply set to sabbath mode.
Testing The Main Control
If the main control is suspected of being faulty, the 
following procedure should be performed to verify main 
control for functionality.
Relay & DC Outputs
One of the primary functions of the main control is to 
operate the multiple relay and DC outputs during each 
cycle. Verify proper operation of these relays using the 
following procedure.
1. Enter “Relay Toggle” through the service menu.
NOTICE
Frequently toggling the compressor relay could 
force the compressor into overload. The 
compressor will automatically deactivate during 
an overload and will remain deactivated until the 
overload switch cools. This could take some 
time. It is important to allow the compressor at 
least 5 minutes off time between relay cycles.
2. Toggle the relay. Its related component should 
activate / deactivate with the switching of the relay. If 
it does not, see “Component Testing.”
Inputs
The main control monitors a number of thermistor inputs 
and switch states during operation. It would be unlikely 
that an error in reading an input would be at the board 
level. Always attempt to replace the faulty switch or 
thermistor input with a known working sample to verify 
proper board operation.
Check Voltage 
At Wall Outlet
Verify Voltage 
At Main Control 
Voltage Input
Check Fuse F1
For Continuity
Open Door.
Is the UI Now 
Functional?
Replace Main
Board
Replace Reed
Switch.
Replace
Fuse
Replace
Power Cord
Alert Customer 
Of Power Failure
Is the Reed
Switch Operating
Properly?
Is the door open? The
Display will not activate
while the door is closed
Inspect Customer UI 
and Data Cable 
Connect Test Display 
To J5. 
Cycle Power And 
Check For Operation 
No Voltage
No Voltage
Voltage
Continuity
Operating
Not Operating
No Continuity
No
No
No
Yes
Yes
Yes
Voltage










