A18
Wolf
External Control / Thermostat Input Fault
Boiler displays A18, no response to room thermostat, heating remains off
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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
Open circuit in room thermostat wiring, Incorrect bridging of external demand terminals, Faulty external thermostat or relay, Misconfigured control parameters
How to Fix / Troubleshooting
Safety: Isolate power before working on low-voltage control wiring.
- Check room thermostat: Ensure it is calling for heat (set temperature above room temperature) and that its display is on.
- Inspect wiring at boiler: Verify that the external demand terminals on the Wolf boiler are correctly wired or bridged according to the installation manual.
- Test with a bridge (technician): A competent person can temporarily bridge the demand terminals to see if the boiler responds, confirming a thermostat or wiring fault.
- Reconfigure controls: Check that the boiler is set to accept external control in its parameter menu.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat / External Control Interface
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