- Boilers
- Gas boiler
E40
Baxi E40 on a gas boiler: heating return NTC sensor faulty
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Baxi E40 means the return NTC sensor is faulty. It is not a reset code: note when it appears, photograph the information menu and call the authorised service centre. The technician checks the return sensor and its wiring.
Safety first
Stop and check this first
- Do not open the boiler to move cables or connectors: Baxi says to disconnect the power before any work and only qualified technicians may work on the appliance.
- If you smell gas: Baxi says to switch the boiler off, not to operate any electrical device or switch on lights, to put out any flame and open the windows. Then leave the home and call your gas distributor's emergency number and the service centre from outside.
Safe checks you can perform
- Smell of gas or combustion fumes
- What Baxi says to do for 40
- Secondary code and reading in the information menu
- Return sensor and wiring checked by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Return NTC sensor measurement
- Do not attempt this professional task: Wiring continuity and insulation
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Return NTC sensor measurement
What they doThe technician measures the return sensor resistance with a multimeter and compares it with the Baxi reference, about 10 kΩ cold at 25 °C, allowing for the actual water temperature.
They must show youthe value measured against the manufacturer's specification and the temperature it was measured at.
In writingthe value and the decision taken.
Wiring continuity and insulation
What they doThe technician checks the continuity of the sensor cable to the board and that there is no short circuit or damaged connector.
They must show youthe cable section or connector checked, with a photo.
In writingwhether the cable was repaired or the sensor replaced, with its part number.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Smell of gas or combustion fumes
- Who:
- you.
- How:
- first, check whether there is a smell of gas or combustion fumes near the boiler, or whether anyone has a headache, dizziness or nausea.
- Result that matters:
- whether it is safe to carry on with the checks for 40.
- If you smell gas:
- do not touch the boiler; follow the gas warning and call from outside.
- If you smell fumes:
- switch the boiler off, open doors and windows and call the service centre, as Baxi says.
- Evidence to keep:
- a note of the time and what you noticed.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
What Baxi says to do for 40
- Who:
- you.
- How:
- in the user table, 40 has no reset: Baxi says to call the authorised service centre. Do not press reset again and again or cut the power to test it.
- Result that matters:
- not wasting time on resets that do not apply to this code.
- If the code stays on the display:
- note the date and time and call the service centre.
- If it clears by itself:
- note it anyway; if it repeats, Baxi says to contact the service centre.
- Evidence to keep:
- photo of the display with the code and the time.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
Secondary code and reading in the information menu
- Who:
- you.
- How:
- press the information key for at least 1 second and find line 00, internal secondary fault code, and line 06, heating return temperature. Leave with the off and reset key.
- Result that matters:
- having the data that goes with 40 for the technician.
- If the reading on line 06 looks impossible or never changes:
- tell the technician, it points to the sensor or its cable.
- If you cannot read it:
- do not change any parameter; a photo of the code is enough.
- Evidence to keep:
- photo of lines 00 and 06 of the menu.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
Return sensor and wiring checked by the technician
- Who:
- Baxi authorised service centre.
- How:
- measures the return sensor resistance, checks the wiring continuity and that there is no short circuit.
- Result that matters:
- whether the sensor or the cable is at fault.
- If the cable is broken or shorted:
- the wiring is repaired and the sensor is kept.
- If the cable is fine and the sensor does not follow the reference:
- the sensor is replaced.
- Evidence to keep:
- job sheet with the measured value and what was repaired.
Baxi says to disconnect the power before any work and only qualified technicians may work on the appliance. Sensors, internal wiring and the board are technician only.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457 · Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Baxi
- Product type
- Gas boiler
Known code variants
- 40
- AEG E40 error
- AEG Fehler E40
- AEG lavadora E40
- AEG lavatrice E40
- AEG lave-linge E40
- AEG Waschmaschine E40
- AEG washer E40
- Baxi 40
- Baxi E 40
- code erreur AEG E40
- E 40
- E40 AEG lavadora
- E40 AEG lavatrice
- E40 AEG lave-linge
- E40 AEG Waschmaschine
- E40 AEG washer
- E41
- Electrolux dryer E40
- Electrolux dryer E40 door
- Electrolux E40 lavadora
- Electrolux secadora E40
- Electrolux tumble dryer error E40
- Electrolux washer 4 beeps
- Electrolux washer door not locking
- Electrolux washer E41 door
- Electrolux washer error E40
- Electrolux washing machine E40
- Error 40 Baxi
- error AEG E40
- error E40 lavadora Electrolux
- error E40 lavadora Zanussi
- error E40 secadora Electrolux
- errore AEG E40
- lavadora Electrolux 4 pitidos
- lavadora Electrolux no arranca puerta
- lavadora Electrolux puerta no cierra
- lavadora Zanussi 4 pitidos
- Neodens Plus 40
- secadora Electrolux E40 puerta
- Zanussi lavadora E40
- Zanussi lavadora E41
- Zanussi washer 4 beeps
- Zanussi washer E40
- Zanussi washer E41
- Zanussi washing machine error E40
What it means
On the Neodens Plus ECO, code 40 is return NTC sensor faulty. This sensor reads the temperature of the water coming back from the heating to the boiler. For 40, Baxi refers to the actions for 20: check the sensor, the continuity of the sensor wiring and that the wiring is not short circuited, with a reference of about 10 kΩ cold at 25 °C, a value that falls as temperature rises. The code does not say whether the sensor, a broken cable or a shorted cable is at fault.
Warnings and stop conditions
- Mediumsource verified
Do not open the boiler to move cables or connectors: Baxi says to disconnect the power before any work and only qualified technicians may work on the appliance.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
- Criticaleditorial warning
If you smell gas: Baxi says to switch the boiler off, not to operate any electrical device or switch on lights, to put out any flame and open the windows. Then leave the home and call your gas distributor's emergency number and the service centre from outside.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
Symptoms and causes
Probable causes · in order
- Return NTC sensor faultyPossible
Baxi says to check the sensor. If its resistance does not follow the manufacturer reference while the cable is sound, the sensor is the cause.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
- Sensor wiring brokenPossible
A loose or corroded connector or a cut cable leaves the circuit open. A continuity test of the wiring separates it from the sensor.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
- Wiring short circuitedPossible
Baxi says to check that the wiring is not short circuited. A bare or pinched cable gives an impossible reading even with a good sensor.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
Virtual technician
Does E40 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
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