LED Trailer lights not working.

[Kiwibacon]

Does anyone have any workarounds or easy fixes for LED trailer lights not working?  Everything works fine on trailers with incandescent bulbs.

 

The LED trailer works perfectly fine on other vehicles, but on the Scout only the brake lights work correctly.  The side/clearance lights flash forever, the indicators don't work.  Didn't check reverse lights.

[Kiwibacon]

Finally found someone else with an issue.  This was a Toureg:  https://www.clubtouareg.com/threads/diy-led-load-resistors-for-trailer-with-led-lights.270393/post-2019911

 

Can anyone tell me about VCDS coding for trailer load monitoring?  I have the VCDS lead.

[Liger1956]

How have the electrics been wired on your Scout? Has the dedicated proper module been used and then coded or has a cheaper method been used e.g. a universal bypass relay?

[langers2k]

Might be worth adding an autoscan too.

 

Assuming it's a proper kit, there are still various versions of the towbar module (hardware/software) that might be installed, I would expect only some will support LED trailer lights.

 

There's also a good change on a pre-FL that none support LED trailer lights...

[Kiwibacon]

20 hours ago, Liger1956 said:

How have the electrics been wired on your Scout? Has the dedicated proper module been used and then coded or has a cheaper method been used e.g. a universal bypass relay?

Dealer installed I presume at purchase time.  I'm the second owner so didn't get to ask those questions.

 

All the Octavia 2 Scout's I've seen here in NZ have the same towbar and wiring package.  It's a locally built tow-bar as we use a different ball size and tongue style to the UK.  Electrically it's a 7 pin flat plug same as Australia which plugs into the car harness somewhere up out of reach.  I know indicators, tail lights and brake light circuits work.  I haven't checked reverse as only my LED trailer has reversing lamps.

 

It's smart enough to tell you if your trailer has an incandescent bulb out or wiring fault.  Also sets off the alarm if you disconnect a trailer while the car is locked.

Edited 5 January, 2021 by Kiwibacon

[Kiwibacon]

19 hours ago, langers2k said:

Might be worth adding an autoscan too.

 

Assuming it's a proper kit, there are still various versions of the towbar module (hardware/software) that might be installed, I would expect only some will support LED trailer lights.

 

There's also a good change on a pre-FL that none support LED trailer lights...

 

Thanks, any idea where to look in VCDS? 

 

If it can't support LED's then I can make up a resistor pack.  But if there is a coding solution it'll be quicker.

[langers2k]

Take a look at the coding and adaptions of '69 Trailer'. If it's likely to be anywhere, it'll be there...

[Kiwibacon]

So this gets more interesting/infuriating.

 

Trailer controller is ANHAENGERELEKTR 001 0020

VAG Number 1K0 907 383

 

I can use output tests to turn on brake lights and blinkers.
I cannot use output tests to turn on the side markers/tail lights.

There are two different reverse light outputs.  "backup lights" which is part of the output tests doesn't work.  But "backup light" on channel 12 is activated when the car is put into reverse (even though the trailer light doesn't light up).

 

The tail-light, stop and indicators all work on an incandescent light board I have when plugged into the same car.
My other euro cars (much older and dumber than the skoda) have two side marker/tail outputs.  Skoda does the same in the controller and maybe the same at the plug.  This isn't the cause of the problem but it may explain wiring faults it displays with some trailers and lack of reversing signal.  I may have some quality multimeter time ahead.

Edited 6 January, 2021 by Kiwibacon

[Kiwibacon]

Just to wrap this up, in-case someone else has been looking for a solution.

 

I made a short tail-light harness with resistor packs for the 4 tail/running lights, reverse lights and indicator circuits with the stop light circuit straight through.  This tricks the Skoda into working perfectly with the trailer and is unplugged the rest of the time.  I used 4x 26 ohm ceramic block resistors that were rated at 21 watt 12v.

Edited 25 September, 2022 by Kiwibacon