Lamp failure control: Functional safety for your LEDs


Properly functioning headlamps and direction indicators are a must for road safety, not just in the dark or bad weather conditions. The many advantages of modern LED headlamps are countered by the disadvantage that a defect in even a single LED can cause the entire headlamp or direction indicator to fail. HELLA has several solutions ready for this potential source of danger – find out what they are.


The key points in short

Defective LEDs represent a potential safety risk: If even one LED is defective, it can mean a failure of the entire headlamp or direction indicator.


Legislators are aware of the danger posed by defective headlamps and flasher units, and accordingly, an acoustic and/or visual warning in the event of LED defects is governed in an EU regulation.


HELLA offers several convincing concepts for monitoring the functionality of LEDs in headlamps and direction indicators: LED flasher unit with ISO pulse, simulation device for cold checking or by LED lamp control units.


LED lamp failed? Modern vehicles report such errors

Despite the longevity of LED lamps and all the care taken during the manufacturing process, defects can still occur in LED headlamps and flasher units.


To counteract this hazard in road traffic, the EU already stipulated in 2016 in Regulation ECE R48 that defects in an LED lamp must be indicated acoustically or visually using an LED failure control by the on-board electronics.

Representation of the power consumption of a light bulb and of an LED lamp with integrated pulse

A Hella LED direction indicator monitors itself and generates a single pulse.

Hella LED direction indicators with integrated electronics for failure control monitor themselves

Solution 1 is ISO 1 32007-1-compliant and focuses on monitoring the LED lamps via the vehicle electrical system.


The self-monitoring LED direction indicators the technology specialist HELLA has successfully established on the market are extremely reliable. Here, the monitoring of the LEDs is realized via an electrical pulse directly in the vehicle electrical system. This ISO 13207-compliant approach requires lamps with integrated electronics for failure control. A single pulse is emitted, which is then evaluated by an electronic ballast. These ballasts simulate an incandescent bulb with an output of 21 watts, and are thus compatible with conventional flasher units. In the event of a defect, the single pulse is not generated, the absence is detected by the ballast and the defect is communicated to the driver via an acoustic and/or visual warning signal. Solution 2 provides for the replacement of the existing flasher unit with an LED flasher unit from HELLA with ISO pulse.


LED flasher unit

This is what an LED flasher unit looks like close up.

Solution 2 involves replacing the existing flasher unit with an LED flasher unit from HELLA with ISO pulse.


The second option is to replace an existing flasher unit with an LED flasher unit from HELLA that complies with ISO 13207. The flasher unit sends 21 watts to the direction indicator in 100-130 ms after each switch-on and uses this pulse to check whether it is still working. With this kind of flasher unit, you can operate bulbs and ISO LED lamps in any combination, since 21 watts correspond to the energy requirements of an incandescent bulb and the flasher unit doesn’t differentiate between the two types of lamps. On the one hand, this is advantageous for vehicles that are operated with frequently changing trailers. On the other hand, manufacturers benefit as they do not have to adapt the electronics of different equipment variants in the lighting each time. The HELLA flasher unit indicates the failure of a lamp by doubling the flashing frequency (E-controller) or switching off the indicator light (P-controller).

Cold check simulation device

This is what the simulation device for cold checks looks like close up.

Solution 3 relies on cold checks by means of a simulation device.


In the case of a cold check, the vehicle electrical system tests the lighting even when it is not actively operating by sending a small test pulse to the lamp. However, this does not work with LED lamps. That is why HELLA offers the simulation device that simulates cold checks to ensure proper operation. This control unit is installed between the body control unit and an ISO 13207-compliant LED direction indicator. If the direction indicator fails, the device stores the last state and displays it at the next cold check.

LED lamp control units for function monitoring

The Basic and Premium LED lamp control units.

Solution 4 implements the monitoring of the LED lamps with the help of an LED lamp control unit from HELLA with ISO pulse.


As a fourth option, HELLA offers two different LED lamp control units: The Basic version monitors only the direction indicators, while the Premium version monitors all light functions. This requires only a single control unit for the right and left, which can be installed quickly and easily thanks to the integrated DEUTSCH connector. To ensure that the LED lamp control unit operates reliably for as long as possible, HELLA relies on active thermal management including overheating protection, sealing against water and dust, and good electromagnetic compatibility.


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