109
Ariston
Zone Output Module Communication Failure
Thermostat shows error 109 and cannot control any heating zones; zone valves or actuators do not respond.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Disconnected zone control module bus cable, Faulty Ariston zone controller, Incorrect addressing of zone modules, Blown low-voltage fuse on zone module
How to Fix / Troubleshooting
Safety: Isolate power to the heating control system and boiler before working on modules.
- Locate zone module: Find the Ariston zone control box (often near the manifold or boiler). Check that its power LED is on.
- Inspect bus cable: Ensure the communication cable between thermostat and zone module is firmly connected and not damaged. Reseat connectors.
- Check addressing/dip switches: Verify that the zone module address (set by DIP switches or rotary selector) matches the configuration in the thermostat installer menu.
- Check fuses: If accessible, inspect any low-voltage fuses on the zone module PCB and replace only with identical rated fuses if blown.
- Reboot system: Power cycle both thermostat and zone module. If error 109 persists, the module may need replacement.
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Repair Difficulty
Hard
4/5
Required Part
Ariston Multi-Zone Control Module
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