Is your LED lighting interfering with the radio? Cause and solution (EMC, ECE R10)

Key points at a glance:

• What EMC interference is and how it occurs
• How to identify, step by step, which light or cable is the source
• How to prevent or resolve radio interference
• What ECE R10 and CISPR 25 certification stand for

Why do LED lighting systems interfere with the radio?

LED lighting operates on the basis of electronic circuits. These circuits control the LED chips efficiently, but may cause unwanted electromagnetic emissions in the process. If the lighting is not adequately shielded, the following systems, amongst others, may be affected:

• FM and AM radio
• DAB reception
• Navigation systems with GPS or GNSS
• Communication equipment
• On-board computers and CAN bus systems

In modern vehicles and machinery, many electronic systems operate in close proximity to one another. As a result, EMC interference can not only be a nuisance, but can also reduce the operational reliability of communication or navigation equipment.

Radiated and conducted interference

There are two pathways through which interference can propagate. Understanding the difference helps in determining the correct solution.

• Radiated interference: the light or LED driver emits electromagnetic energy which is picked up by an antenna or receiver.
• Conducted interference: the interference propagates via the vehicle’s power supply, mass or wiring harness.

Installation also plays a key role. A poor mass connection, poor cable routing, cable loops or an antenna situated close to power cables can exacerbate the interference.

Why multiple lights can exacerbate the problem

If you switch on several lights at the same time, the overall level of interference may increase. Furthermore, the luminaires often share the same power supply and mass. As a result, interference is sometimes only noticeable when an entire light bar or set is switched on.

How to determine whether the LED lighting is the cause

Would you like to know which light or component is causing the interference? Then work systematically from the possible source of the interference back towards the installation. By following the steps below, you can avoid replacing components unnecessarily straight away.

1. Switch the suspect lighting off and on again, and check whether the interference occurs at the same time.
2. Truck each light individually to isolate the potential source of interference.
3. Truck FM and DAB separately and check different frequencies or stations.
4. Check whether the interference changes when the engine is switched on or off.
5. Check ground connections, connectors and power cables.
6. Keep power cables and aerial cables separate wherever possible.
7. Temporarily connect a different light to the same connection point to compare the results.
8. Please consult the technical documentation to check how the lighting has been assessed for EMC compliance.

Common causes of radio interference

Most interference problems can be traced back to a limited number of possible causes. The table below links common symptoms to a probable cause and a practical initial check.

Symptom	Probable cause	Initial check
Symptom: Noiseor crackling on FM as soon as a light switches on	Probable cause: Emissions from the LED driver or interference transmitted through the electrical system	Initial check: Truck the lights individually
Symptom: DAB receptioncuts out	Probable cause: Insufficiently shielded driver or poor installation	Initial check: Truck a different light on the same connection point
Symptom: GPSor GNSS reception deteriorates	Probable cause: Source of interference close to the antenna or antenna cable	Initial check: Temporarily increase the distance between the power supply and antenna cables
Symptom: Interference increases as more lights are switched on	Probable cause: Higher overall interference level or an issue with the shared power supply or mass	Initial check: Check the power supply and mass connections
Symptom: The fault only occurs when the engine is running	Probable cause: Possibly another or additional source of interference	Initial check: Compare the situation with the engine on and off
Symptom: Fault occurs after replacing halogen with LED	Probable cause: The switching LED driver generates electromagnetic emissions	Initial check: Check the EMC status and documentation for the light

Resolving radio interference caused by LED lighting

Tackle the problem in ascending order, from simple checks to replacing the source of the interference. This way, you’ll avoid replacing parts when the actual cause lies within the installation.

1. Check the lighting: identify which light is causing the interference and check whether it has a valid ECE R10 approval or supplementary EMC assessment.
2. Check the mass connections: repair any faulty, dirty or loose mass connections and inspect the connectors.
3. Optimise cable routing: keep power cables and antenna cables as far apart as possible and avoid them running parallel to one another for long stretches.
4. Use shielded cabling only where appropriate: ensure the shielding is connected in accordance with the vehicle manufacturer’s instructions or those of an EMC specialist.
5. Add targeted filtering: in specific cases, ferrite cores or suitable EMC filters can help suppress conducted interference. The filter must be suited to the frequency, current and installation.
6. Replace the source of interference: if a single specific light remains the cause, replace it with an alternative that has been demonstrably assessed against the relevant EMC requirements.

A ferrite core or EMC filter may help, but it is not a universal solution and should not be used as a substitute for a properly fitted light and installation. If this does not resolve the issue, there may be another electrical or electronic problem.

If you’re not experiencing static or loss of reception, but are seeing an error message, hyperflashing or flashing lights, please refer to our article on CAN bus interference caused by LED lighting.

What do ECE R10 and CISPR 25 say?

ECE R10 and CISPR 25 help to minimise the risk of electromagnetic interference, but are no substitute for an assessment of the entire installation.

UNECE R10 sets out EMC requirements for vehicles and for electrical or electronic vehicle components. A light with a valid R10 approval has been assessed against the relevant EMC requirements in accordance with the applicable truck methods.

CISPR 25 sets out truck methods and emission limits for electromagnetic disturbances that may affect on-board radio and other receivers. The standard defines various emission classes, with Class 5 imposing the strictest limits.

Please note: a CE marking is not the same as a vehicle-specific approval in accordance with UNECE R10. The CE marking may indicate that a product complies with applicable European product legislation, but does not in itself constitute proof that vehicle lighting has been approved in accordance with R10.

Even a valid R10 approval does not guarantee that every vehicle configuration will remain completely interference-free. Cable routing, mass, antenna position and the combination of components also play a role. You can read more background information in the explanation of EMC interference suppression and the comprehensive article on CISPR 25.

Radio interference or a CAN bus problem?

Not every interference that occurs after fitting LED lighting is an EMC problem. The nature of the symptom often indicates where you should look for the cause.

• Noise, crackling or loss of signal: this usually indicates electromagnetic interference affecting the reception of FM, DAB, GPS, GNSS or communication equipment. In such cases, check the light, earth connection, cable routing and EMC assessment.
• Error message on the dashboard: the vehicle may not recognise the lower power consumption of LED lighting and may incorrectly interpret the light as faulty.
• Flashing lights or momentary flashes: this can be caused by the pulses the vehicle uses to check whether the lighting is still working.
• Hyperflash on indicators: the indicators flash more rapidly because the lamp monitoring system detects that the electrical load is too low.
• Failure of trailer or trailer lighting: the control system of the towing vehicle and the trailer lighting system may not be working together correctly.

Dashboard warnings, hyperflashing and flashing lights are often attributed to CAN bus issues. Technically speaking, the cause usually lies not in the CAN bus communication itself, but in the electronic lamp monitoring and the different power consumption of LED lighting.

Do you recognise these symptoms? Then read on to find out how to identify and resolve a CAN bus fault caused by LED lighting. Would you first like to know what manufacturers mean by this commonly used term? Then take a look at our explanation of canbus proof LED lighting.

TRALERT® solutions compliant with CISPR 25 Class 5

TRALERT®’s vehicle lighting is selected and assessed against the relevant EMC requirements where applicable. For applications with heightened EMC requirements, selected products within the range are available with a verifiable CISPR 25 classification. These products are suitable for applications involving sensitive communication, radio or navigation systems.

One example is the WF-8082 LED work light:

• Tested to CISPR 25 Class 5, the strictest emission class
• Robust, heavy-duty housing
• IP69K, resistant to high-pressure and high-temperature water jets
• An ADR-compliant version is also available within the series

In the TRALERT® product shop, you can easily filter by EMC certification, allowing you to quickly select the right lighting based on the required standards.

Frequently asked questions about radio interference caused by LED lighting

Why do LED lighting systems interfere with the radio?

LED lighting is controlled by a switching driver. This circuit can generate high-frequency electromagnetic energy which is picked up by the receiver’s antenna or wiring. If there is insufficient interference suppression or the installation is sub-optimal, this can manifest as noise, crackling or loss of reception.

Can LED lighting also cause DAB or GPS interference?

Yes. Depending on the emissions and their harmonics, DAB reception may be lost or GPS and GNSS reception may be weakened. The likelihood of interference may increase if the source of interference, the power cable or the driver is located close to the antenna or antenna cable.

How do I identify which LED light is causing radio interference?

Switch the lighting off and on again, then truck each light individually. Next, check the mass, connectors and cable routing. If possible, temporarily connect a different light to the same connection point to determine whether the light or the installation is causing the interference.

Does a ferrite core always solve radio interference?

No. A ferrite core can attenuate certain shapes of conducted interference, but it is not a universal solution. If the cause lies with the light, a poor mass connection or unfavourable cable routing, these issues must be addressed first.

What is the difference between ECE R10 and CISPR 25?

ECE R10 sets out EMC requirements for vehicles and electrical or electronic vehicle components. An R10 approval can be identified by an E-mark bearing the designation 10R. CISPR 25 describes truck methods and emission limits for interference that may affect on-board receivers. Class 5 applies the strictest limits in this regard.

Choose lighting that doesn’t interfere with your electronics

Are you looking to select lighting for a vehicle with sensitive on-board electronics? Then don’t just look at the light output and protection class; also check the available EMC approvals and truck data. If you’re unsure about the right solution for your vehicle or application, the specialists at TRALERT® will be happy to advise you.