Thermostat displays E10 and indicates an external sensor fault; remote room sensor readings are missing.

Safety first: Turn off HVAC power at the breaker before working on sensor wiring.

• Step 1 – Identify sensor terminals: On the Geo wall plate, locate the dedicated S1/S2 or RS+/RS− terminals used for remote sensors (exact labeling varies by model).
• Step 2 – Check connections: Ensure the remote sensor wires are firmly clamped in the sensor terminals and that there are no stray strands touching adjacent terminals.
• Step 3 – Inspect sensor location: At the remote sensor, remove the cover and verify the wires are secure and the sensor is not damaged or exposed to moisture.
• Step 4 – Continuity test: With power off and sensor disconnected at both ends, test continuity of each sensor conductor with a multimeter. Repair or replace the cable if open.
• Step 5 – Verify sensor type: Confirm that the sensor is a Geo‑approved remote sensor with the correct resistance/communication type. Using a non‑compatible sensor can trigger E10.
• Step 6 – Replace sensor: If wiring is good but E10 persists, replace the remote sensor module with a new Geo‑compatible sensor.