Error A16, unit may not respond to thermostat or user commands.

Safety: Turn off power before altering low‑voltage control wiring.

• Check thermostat: Ensure the room thermostat or remote control is powered, set to heating mode, and calling for heat.
• Inspect wiring: At the Fondital terminal strip, verify that thermostat wires are firmly connected and not broken.
• Bypass test: Temporarily bridge the thermostat terminals at the heater (if allowed by the manual). If the unit starts, the thermostat or its wiring is faulty.
• External module: If using an OpenTherm or proprietary Fondital controller, check its display for errors and reset it according to its manual.