Code 05 displayed, furnace does not respond to thermostat demand

Safety: Isolate power before removing covers or touching wiring.

• Locate the flow sensor: On Vokera hydronic furnaces, the flow NTC sensor is usually clipped or screwed into the flow pipe leaving the heat exchanger.
• Check connection: Ensure the sensor plug is fully seated on the sensor and on the PCB. Look for corrosion or broken wires.
• Inspect sensor body: Check for signs of leakage around the sensor pocket or physical damage.
• Basic resistance check (for qualified persons): With power OFF and wires disconnected, measure resistance across the sensor. Compare to Vokera service data for the current temperature. If reading is open or near zero ohms, the sensor is faulty.
• Replace if needed: If the sensor is clearly defective, it should be replaced with a genuine Vokera flow NTC sensor. Drain the system if required before removal.