A421 Series Controls display fault codes on the LCD as described in the following table.
| Fault code | Definition | System status | Solution |
|---|---|---|---|
| SF flashes alternately with OP | Open temperature sensor or sensor wiring | Output functions according to the selected SF mode | See Troubleshooting procedure. Cycle power to reset the control. |
| SF flashes alternately with SH | Shorted temperature sensor or sensor wiring | Output functions according to the selected SF mode | See Troubleshooting procedure. Cycle power to reset the control. |
| EE | Program failure | Output is off | To reset the control, press MENU. If problems persist, replace the control. |