Trailer LED's pulse faintly when connected
 

Reaching out to Rennlist to see if anyone else has had the issue and/or solved it.

2014 VW Touareg TDI, factory tow package
2015 Trailex 7541 EB

When we connect the trailer's 7 way plug to the Touareg, the LED's on the trailer pulse faintly and quickly. We get no error codes on the dash. When the parking lights of headlights are on, all lights function as they should on the trailer. We were informed that this is a German vehicle issue, and were advised to purchase a special adapter. We tried two, the TowReady and the Curt. Neither solved the problem. The lights pulse more faintly with the adapter installed, but we still get the faint pulsing.

Others we have spoken to said that none of the lights worked as they were supposed to, but that is not our issue.

We contacted Trailex, as well as reaching out to several VW, Porsche and Audi service departments, but no help there.

Any help would be greatly appreciated, as this seems to have many folks stumped. Someone must have the answer.

Thanks

Are you sure it's a factory tow pkg? Is it possible that it's the OEM parts, but added after delivery and not coded correctly?
It kinda sounds to me like the type of thing that would happen if the wiring had been spliced into the factory taillight harness. The trailer lights might flicker because they're receiving a PWM signal that is intended to be used to drive the LEDs in the vehicle tail lights. If used with non-LED trailer lights the flickering would be much less noticeable, if at all. That scenario would explain the behavior of the adapters you purchased, why the vehicle is never giving a bulb out error, and why they dont pulse when the headlights are turned on.

Unless you're positive that it's a factory tow pkg, with the correct towing module that's been enabled via coding (not just a factory hitch with retrofit wiring) I'd start my investigation there. On my tiguan a vagcom scan will give a list of all the modules that are installed in the car and if the tow module is one of them. That last part is likely the same for the touareg, but I'm not 100%.

Thanks for the reply. According to the window sticker, the tow package was factory installed.

We'll try and find someone with a vagcom and take it from there.

Thanks again.

I have the same trailer and tow with a ML350 Bluetec. I only get the pulse when trailer is plugged in and the car is NOT running. I unplug the trailer When not towing, but don’t bother when I stop for lunch etc

Yoy might have the same issue

Thank you ... Worth a try .

Will report back :)

I have a Cayenne diesel with factory tow package and a Trailex open trailer. Same behavior. No issues with trailer lights or dashboard warnings. I assumed this is correct behavior, possibly how the vehicle's towing electronics determine if the trailer lights are functional. Also, the vehicle alarm is triggered if the trailer is disconnected while the vehicle is locked. From the manual:

Trailer Hitch pg.242 Unhitching a trailer …Trailer Hitch Always turn the alarm system off before unhitching the trailer because otherwise the alarm is triggered when the plug is removed.

Steve,

Thank you ! Good to know and good advice .

I certainly hope this thread helps others with the same problem .

I believe this is a known issue for VW/Porsche cars and is related to how the tow vehicle deals with LED trailer lights as part of an algorithm to identify inop trailer lighting bulbs. On my Cayenne, which had a factory tow package, it was simply a coding issue. There are also trailer connectors you can buy on Etrailer that deal with LED trailer lighting. Search the Cayenne forum for more info.

Frank

Thank you for your input ... Much appreciated . We have tried two of the LED light adaptors . One from the Tow Ready company and the other from Curt manufacturing . Neither seemed to make any difference in the behavior of the LED's pulsing.

We just tried. Pulsing lights whether vehicle is running or not.

With the Curt adapter, the lights are fainter, but still pulsing.

Still waiting to hear from VW service people.

same thing on my '16 cayenne and trailex
never figured out a real answer to the problem (tried the "adapters", no luck)
I just deal with it and let them blink
hopefully you can figure it out

It looks like that’s where we’re at too. We’ll keep,trying to see if anyone may have an answer. It’s not like we can’t use the trailer.

I have a Cayenne 08TT with factory tow -- I only notice this when the trailer is connected but the vehicle is not running (and likely locked -- but I haven't confirmed). Alarm will trigger if you pull the plug in this configuration.

I figured it was a safety feature...

I have not noticed this while the vehicle is running.

Mike

The vehicle is probably sending small currents to the trailer for one of two purposes: 1) to check for blown bulbs, or 2) as part of the vehicle alarm - i.e. If the current does not flow, it assumes the trailer has been removed (try pulling the plug with the car locked and alarm on). Not sure if it is something that can be coded out, but that is what I would check.

Marc,

Thank you ! You would think that maybe this could be coded for a fix . I did forward this thread to a Porsche dealership for hopefully some ideas .