Interference with truck and trailer lighting: diagnosis and solutions

You can usually trace interference in truck or semi-trailer lighting in four steps: first check the connectors and cables, then measure the voltage with a multimeter, check the resistance and, finally, truck the earth connection. This allows you to detect corrosion, cable breaks, voltage loss or a poor mass more quickly. If an LED light continues to display an error message without any visible cable fault, load detection is often the cause. You can read more about this in our article on CAN-bus interference in LED lighting.

In this blog, you will read how to:

• Interference can be addressed: flickering, moisture problems and CAN-bus interference.
• Quick diagnosis: practical steps for efficient testing of cables and systems.
• More about plug & play solutions: complete systems that make your work easier.

Types of wiring harness interference

Wiring harnesses are the backbone of any lighting system. Common causes of interference are:

1. Bad connections: Corrosion or loose connectors interfere with the power supply.
2. Wear and tear: Vibration and temperature changes damage insulation and wiring.
3. Overload: A cable that is too thin leads to voltage loss and overheating.

Step-by-step diagnosis of wiring harness problems

1. Visual inspection: Check connectors for corrosion or loose connections. Look for damaged cable insulation.
2. Truck the voltage: use a multimeter to measure the voltage at each end point. A deviation indicates a cable or connection problem.
3. Check the resistance: Measure the resistance in the cable. A value higher than 0.5 ohms indicates wear or corrosion.
4. Check grounding: Use a voltage meter to truck whether the grounding is functioning correctly.

No cable fault found, but still getting an error message?
If the four steps do not resolve the issue, even though the vehicle is displaying an error message regarding the LED lighting, the cabling is usually not the problem. The vehicle’s electronics interpret the low power consumption of the LED light as a fault. This is a matter of load detection, not a cabling fault.

Prevention tips:

• Always choose the right cable thickness. For a 10 amp light with a cable length of 3 metres, a cable with a cross-section of 1.5 mm² is ideal. For longer cables (>5 metres), at least 2.5 mm² is required.
• Protect wiring harnesses from mechanical stress with cable ducts or additional insulation layers.
• Use waterproof connectors such as SuperSeals connectors to avoid moisture and corrosion. A common cause of interference is a poor or damp plug connection. Many lighting systems therefore use a waterproof SuperSeal connector to protect the electrical connection.
• Moisture infiltration is a common cause of interference. Therefore, choose lighting with a high IP value for maximum protection against moisture and dirt infiltration. For performance in the harshest conditions with lots of dirt and moisture, a product with IP69K is the best choice.
• Of course we assume that cables are connected according to the correct wiring scheme for truck lighting

Other problems you may encounter with semi-trailer lighting:

Flickering lighting

• Cause: Poor mass, voltage fluctuations or incompatible CAN-bus systems.
• Solution: Check that the lighting is compatible with the electrical system and truck the wiring for loose connections.

Overheating

• Cause: Poor ventilation or excessive load on the system.
• Solution: ensure adequate heat dissipation and use wiring with the correct cable thickness.

Colour changes

• Cause: LED ageing, poor power supply or faulty drivers.
• Solution: Check the power supply and replace LEDs that no longer comply with the original colour values.

Moisture problems

• Cause: Poor sealing of connectors or damaged cable insulation.
• Solution: use high-quality connectors (IP67 or higher) and protect cables with heat-shrink tubing if necessary.

Problems with lighting functions

• Cause: broken lights, bad wiring or interference in the electrical system.
• Solution: Check with a multimeter that voltage is present at the correct points. Inspect the wiring for damage and replace faulty connectors. If the problem lies with the system, a CAN-bus control box can help pass on the right signals and prevent interference.

The importance of ECE and CE certified products

Working with ECE-compliant products not only guarantees that your lighting is legal, but also minimises the risk of technical interference. TRALERT®'s lighting products comply with these standards.

This ensures that wiring and connectors meet the requirements of ECE R10 (electromagnetic compatibility).

Save time with lighting sets

As well as bespoke solutions, TRALERT® also offers a range of ready-made lighting sets. Ideal for standard trailers. Also ideal for replacing old lighting. TRALERT®’s lighting sets are complete lighting solutions and contain everything needed to equip your vehicle with safe, high-quality lighting. These sets have been carefully put together by TRALERT®’s LED specialists. Particular attention has been paid to regulatory compliance, ease of connection and product quality.

Customised lighting solutions for 24 Volt systems such as heavy transport & semi-trailer construction

At TRALERT®, we are ready to support you with innovative solutions for any lighting system. Our plug systems, robust wiring harnesses and SuperSeal connectors are designed to make installations easier and fault-free.

Benefit from:

• Technical support: from drawing board to installation, we think along with you.
• Access to the dealer portal: for loyalty-based pricing, quotations and insight into your orders.

Check out the possibilities of becoming a TRALERT® partner.