6. Alarm Signals
In the event of operation outside of normal parameters, the control board identifies the issue with an alarm signal. The alarm signal and temperature are displayed in
| Alarm Signals | |
E1 | High Temperature Alarm | |
E2 | Low Temperature Alarm | |
E3 | Defrost Alarm (cabinet only) | |
E4 | Not Used | |
E7 | High Condenser Temperature Alarm | |
(clogged filter) | ||
| ||
E8 | Defrost Thermistor Malfunction Alarm | |
E9 | Condenser Thermistor Malfunction Alarm | |
EA | EEPROM Write Error Alarm | |
ED | EEPROM Verification or Read Error Alarm |
7. Control Board Check Procedure
Before replacing a control board that does not show a visible defect and that you suspect is bad, always conduct the following check procedure. This procedure will help you verify your diagnosis. Before you begin the diagnostics, verify proper supply voltage and that the unit is correctly plugged in.
1)Move the power switch to the "ON" position and the rail switch to the "NORMAL" position. Both cabinet and rail temperatures should be displayed. The perimeter heater, cabinet fans, and rail fans should be on.
2)If the temperature display is not on, check the 3A 125V fuse on the control board and the control transformer secondary circuit. Secondary transformer output is 10V at
115V primary input. If the fuse and the secondary circuit voltage are good, but the temperature display is off, the control board is bad and should be replaced.
3)If the temperature display is on and the components are not energizing, verify 12VDC to the corresponding relay. If there is no voltage to the component relay, the control board is bad and should be replaced.
8.Control Board Replacement
1)Open the front panel. Move the power switch to the "OFF" position, then unplug the unit.
2)Remove the wire cover, then remove the control box cover.
3)Disconnect the control board wire connectors.
4)Remove the control board.
5)Install the new control board in the control box taking care not to damage it.
6)Connect the control board wire connectors to the new control board.
7)Replace the control box cover in its correct position.
8)Plug in the unit, then move the power switch to the "ON" position to start the unit's cooling process.
9)Check the setpoint and service menu settings and verify that they are set to the factory defaults. See "II.D.4. Controls and Adjustments" and "II.D.5. Service Menu."
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