Display shows E13, furnace may run at limited output

Safety first: Isolate power before working on low-voltage sensor wiring.

• Locate outdoor sensor: Find the Remeha outdoor sensor on an external wall, away from direct sunlight and heat sources.
• Inspect cable: Check the cable from the sensor back to the furnace for damage, joints, or water ingress.
• Terminal check: At the furnace, ensure the sensor wires are firmly clamped in the correct terminals.
• Measure resistance: Disconnect the sensor and measure its resistance at ambient temperature. Compare with the Remeha NTC chart. Replace if out of range.
• Control settings: If no outdoor sensor is installed, ensure that weather-compensation is disabled in the installer menu to avoid E13.