Display shows “H0” or “HO” and unit appears locked or in hold mode

Safety: No internal service required.

• Exit hold mode: Refer to the Autotrol control manual for your model. Typically, pressing and holding the regeneration or program button for several seconds will exit hold/vacation mode.
• Check installer settings: Enter the installer menu and verify that any service hold or vacation settings are disabled.
• Factory reset: If you cannot exit hold mode, perform a factory reset and reprogram the unit.
• Board replacement: If the display remains stuck in “H0” despite correct programming, replace the electronic control board.