CALX Comm. Error I/O Daughter Board (Advisory)
To avoid serious injury follow all warnings and instructions in the manual. Wear appropriate personal protective equipment.
| Cause | Solution |
| No AC power to the AMZ DB | Verify the AMZ DB is turned on by confirming the disconnect switch on the heat box is in the ON position. |
| AC disconnected switch broken | Disconnect the AMZ DB from AC power. Check wiring to the switch. If wiring is good, replace the AC disconnect switch of the heat box. |
| Faulty AMZ DB control board | Replace the AMZ DB control board. |