Error E10

Safety precautions

1. If you smell gas, do not touch the boiler. Ventilate the area, turn off the gas supply at the meter if safe to do so and call your gas emergency number and a Gas Safe engineer. 2. Isolate electrical power to the boiler before opening covers. Only a qualified person should work on live mains or gas components. 3. Do not bypass safety devices, tamper with the gas valve, or attempt complex electronic repairs yourself.

Initial checks a homeowner can do

1. Note the exact error and any other codes shown. Try a simple reset by pressing and holding the boiler reset button for 5 to 10 seconds. Wait for the boiler to restart and see if E10 clears. Do not keep resetting repeatedly if the fault returns. 2. Visually inspect the outdoor sensor and wiring route. The sensor is usually mounted on an external wall or wired to a probe socket. Look for obvious damage, disconnection, crushed cable, or signs of rodent chew. 3. Check the boiler display and user manual to confirm the outdoor probe location and connector on the PCB or terminal block so you know what to inspect next.

Specific diagnostic and fix steps (use a multimeter if comfortable and competent)

1. Turn off power to the boiler at the isolator and allow internal parts to discharge. 2. Locate the outdoor sensor connection. That may be at a terminal on the boiler's PCB or a connector on the external probe. Refer to the boiler manual for the correct terminal. 3. With the sensor disconnected from the boiler, measure its resistance with a multimeter on the ohms setting. Most Baxi NTC outdoor probes are specified in the manual (common value is around 10 kΩ at 25°C but check your manual or NTC chart first). Note that an NTC sensor decreases resistance as temperature rises. 4. Verify the sensor resistance changes with temperature: warm the sensor slightly with your hand and see resistance drop, then cool it and see resistance rise. If the resistance is open-circuit (OL) or shorted (very low near 0 ohms) the sensor is faulty and should be replaced. 5. If the sensor reads correctly, check continuity of the wiring between the sensor and the boiler connector. With power off use the multimeter continuity function to check for breaks. Also inspect the connector for corrosion or loose pins. 6. If wiring is intact at both ends, connect the sensor back and check the connector at the PCB for a secure fit and no corrosion. Power the boiler back up and observe the display and any live sensor voltage if documented in the service manual. 7. If sensor and wiring are good but the boiler still shows E10, the PCB input circuit may be faulty. Further electronic diagnosis and PCB replacement must be carried out by a qualified engineer.

When to call a professional

1. Call a Gas Safe registered engineer if the sensor needs replacing, wiring runs through walls or is damaged, the PCB is suspected faulty, or if you are not competent or confident using a multimeter. 2. Call immediately if you smell gas, see signs of burning, smoke, or other safety-related faults. 3. Inform the engineer that the boiler showed E10 (outdoor sensor) and what tests you have already performed to speed up diagnosis.

Additional notes

1. A single reset may clear a temporary reading glitch, but repeated resets are not advised. 2. Keep the boiler manual or NTC sensor chart to hand when testing so you compare measured ohms with the correct specification. 3. Replacing the outdoor sensor is usually a straightforward job for an engineer, but if the fault is on the PCB that will require professional replacement and testing.