Car blinking trailer lights

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notso9bit
Posts: 3
Joined: 21 Apr 2022, 14:49

Car blinking trailer lights

Post by notso9bit »

When trailers using LED lights are connected to this car, it will flash one or both sides very consistantly.
Very random and inconsistent things will make it stop. For example turning on the wipers or turning on the parking break will make it stop blinking,but those dont always work. Like i mentioned this does not happen with trailers that dont use LED lights.

also, no.. the indicator is not on. this happens constantly, and infact sometimes indicating will make the blinking stop.

car is a 2011 508 2L diesel

here is a link to a video showing the problem
Last edited by myglaren on 21 Apr 2022, 16:06, edited 1 time in total.
Reason: Video Link
Hell Razor5543
Donor 2021
Posts: 12487
Joined: 01 Apr 2012, 09:47
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Re: Car blinking trailer lights

Post by Hell Razor5543 »

Some LEDs have 'load' resistors so that the relevant ECU 'thinks' it is 'seeing' a filament lightbulb, and so it is managed properly. However, some LEDs DON'T have the 'load' resistor so (to all intents and purposes) it appears to the ECU as though there is a short circuit, causing issues. The two things I would suggest you try is to (if the socket will allow you) turn the LED around (this has been known to work, but not always), and to see if the LEDs have the 'load' resistors (if they don't consider replacing them with ones that do, to see if that helps). The fact that trailers with filament lightbulbs don't cause problems clearly indicates the LEDs are the cause.
notso9bit
Posts: 3
Joined: 21 Apr 2022, 14:49

Re: Car blinking trailer lights

Post by notso9bit »

Hell Razor5543 wrote:
21 Apr 2022, 16:13
Some LEDs have 'load' resistors so that the relevant ECU 'thinks' it is 'seeing' a filament lightbulb, and so it is managed properly. However, some LEDs DON'T have the 'load' resistor so (to all intents and purposes) it appears to the ECU as though there is a short circuit, causing issues. The two things I would suggest you try is to (if the socket will allow you) turn the LED around (this has been known to work, but not always), and to see if the LEDs have the 'load' resistors (if they don't consider replacing them with ones that do, to see if that helps). The fact that trailers with filament lightbulbs don't cause problems clearly indicates the LEDs are the cause.
Im sure youre correct, because I measured the voltage going into the ecu and coming out, and its only blinking on the output side. But the problem is that I use many different trailers (some owned by me some not) and most have led fittings (as almost all newer trailers do). not interchangeable bulbs.

What can I do about this? is there a different ecu I can install that is made to work with LED and doesnt interperate them as a short?

We actually have another of the exact same car (but smaller engine) and it works with all trailers LED or not :/
Hell Razor5543
Donor 2021
Posts: 12487
Joined: 01 Apr 2012, 09:47
x 1673

Re: Car blinking trailer lights

Post by Hell Razor5543 »

Some bulbs are 'capless' (such as the W5W) and so can be pushed onto their socket one of two ways. With a normal filament bulb this is not a problem, but some LEDs don't 'like' this. If any LEDs are 'capless' see if they have a varying resistance (if left to right has a different resistance than right to left, as diodes are 'valves' and only let power 'flow' one way), and, if they do, see what happens if you rotate them 180 degrees in their sockets.
notso9bit
Posts: 3
Joined: 21 Apr 2022, 14:49

Re: Car blinking trailer lights

Post by notso9bit »

Hell Razor5543 wrote:
21 Apr 2022, 17:57
Some bulbs are 'capless' (such as the W5W) and so can be pushed onto their socket one of two ways. With a normal filament bulb this is not a problem, but some LEDs don't 'like' this. If any LEDs are 'capless' see if they have a varying resistance (if left to right has a different resistance than right to left, as diodes are 'valves' and only let power 'flow' one way), and, if they do, see what happens if you rotate them 180 degrees in their sockets.
Hi. the led fittings dont have a "socket" as they are their own sealed unit.

However I have found products that act as a 13pin-13pin adapter and introduce load to each pin. So I will test that out, and reccommend anyone to do so if they have this problem in the future.