Hunter EC Controller Shows "J4 AC" Error and Switches to Military Time

Fixing ERR 4 and Time Format Issues on a Hunter EC Controller

A Hunter EC controller displays a blinking "J4 AC" (interpreted as ERR 4) and the time format unexpectedly switches to military time. The system won't start automatically or manually.

What ERR 4 Means

ERR 4 indicates a short circuit in the wiring to valve #4 or a shorted solenoid on that valve. The solenoid should be tested and replaced if necessary.

Reset and Reprogram Steps

1. Remove the backup battery from the lower compartment.
2. Disconnect power to the controller.
3. Reapply power.
4. Hold down the negative, forward arrow, and PRG buttons simultaneously.
5. Press and release the reset button in the lower compartment.
6. Release the three buttons; the time should revert to 12:00 AM.
7. Reprogram the controller with the desired 12‑hour (AM/PM) format—refer to the manual for the setting.

If the display remains garbled after a full power cycle and reset, the controller may be damaged and require replacement.