A controller with a partial or blank display usually has damage to an electronic component on the internal circuit board. Normally this type of damage cannot be repaired. If the controller was installed outside be sure that the door remains closed completely when left unattended. Moisture intrusion is one of the more common reasons this problem may occur.
- Some other reasons for a damaged display are voltage surges and lightning. Bad wire connections on the controller's primary power side can also create issues.
- A problematic display may be the result of the controller reacting to a field issue. If a short in the valve field wiring is substantial enough, it could cause damage to the internal circuit board. Be sure to check all connections thoroughly.
On some Hunter controller's a 9 volt battery can be installed in the face panel. A working face panel will display a NO or NO AC message after a fresh 9 volt battery is installed.