Trailer Light Wiring Passat 3B

Hello,
I'm hoping to find help here, as I wasn't able to get help from our local .
I retrofitted a trailer hitch with a 13-pin electrical kit from VW to my Passat 3B, manufactured in 1998. A failure of a turn signal on the trailer is indicated by this electrical kit through an increased blinking frequency, which works reliably. However, I would still like to have an optical check in the instrument cluster. Therefore, I replaced the standard hazard light switch with one that has a trailer control function, but unfortunately, the illumination in the instrument cluster now blinks when the hazard lights are activated ! My idea that the connection on the control unit, where the illumination is now connected, is also used for the control light in the instrument cluster, has not been confirmed, because nothing blinks when a trailer is connected .
'Does anyone have any advice? Retrofitting a trailer hitch is actually quite a common procedure.'
As I said, my local dealer can't/won't help (they want me to leave the car there), and besides, I'd have to drive there for the umpteenth time (over 30 km), and I'm fed up with them! If they told me I needed another cable, I'd buy it from them without complaint, but I wouldn't let them install it.

Okay, and finally: WBS (Work Breakdown Structure) number: 3BO 953 235 B. WL + BL + DI (what does that even mean?).
new 3BO 953 235 E WBS + AK + OMR
-Sentence: 3BO 055 204 B

Best, Sascha.

Does anyone have any advice? Or have I missed something in the forum, so that no one wants to respond? I would be grateful for any tip, no matter how small!

Best, Sascha.

Hi,

Perhaps you should allow more than 12 hours.

I would say: Just don't do it. The effort involved is enormous compared to the benefit – for example, you're missing the individual wires that connect to the turn signal contacts on the AH socket, and I think it's anything but easy to figure out the correct codes and pin assignments for the involved control units.

I also have the retrofit version without the AH turn signal indicator, but with additional technology instead – it works well and reliably.

If you want more... then just connect it to the AH-LED, and that's it.

Overall, for me, this falls into the category of "minor" or "trivial" tuning.

Best regards,

Jan.

HI,

The AHK (trailer wiring harness) relay detects the additional load of the trailer lights through the increased current draw. It is normal for the turn signal light to illuminate when the hazard lights are activated. However, from what I understand, in your case, the (low beam/parking) light is also on. The only solution seems to be comparing the wiring diagrams.

Hello,

Yes... I'm a little impatient. Sorry!

'No, it's not the headlights or parking lights that are flashing, but only the night illumination/lighting of the instrument cluster (no other switch or warning light is affected). And this happens even when there is no trailer attached! The flashing function itself works with both switches, both with and without a trailer - only the trailer indicator LED in the instrument cluster doesn't work. A friend had a tow hitch retrofitted to a '99 Bora, but in a workshop. In that case, the instrument cluster's trailer indicator LED works. However, his trailer connector is 8-pin, and it doesn't fit otherwise.'

As far as I know, and according to the information from my VW dealer, there are only 2 switches available, either with or without trailer hitch control - but both are 7-pin! Where would additional cables come from the back, especially since the cables of the wiring harness are only connected to the taillights? }

It might be considered a minor adjustment, but I would still like to get an estimate of the effort involved (if anyone knows the solution or at least an approach) so I can decide for myself whether or not I want to proceed.

What I can't quite understand is the fact that there's a voltage pulse on the connection of the new WBS (only when the hazard lights are on), where the voltage for the instrument lighting (gray/blue) is connected, especially since that also works with the new unit. Unfortunately, my 'How it's done' manual doesn't have a wiring diagram for vehicles with AK (presumably referring to an electronic control unit).

That being said: good night.

Best, Sascha.

Hello there,

Okay, I successfully installed the tow hitch in my 1999 Passat, including the turn signal indicator in the instrument cluster.
The warning light relay for towing hitches and the standard warning light share the same terminal.
The contact that serves as the input for the switch illumination on a standard hazard light relay becomes the output on a trailer hitch (AHK) hazard light relay, which controls the indicator light. This is why your instrument lighting also blinks.
The warning light for the trailer hitch is illuminated as soon as the ignition is turned on, and its brightness cannot be adjusted.
You need to connect a wire from the relay to the blue connector on the instrument cluster.
The bulb/diode was already installed in my car.

I don't know which connections need to be made there at the moment.
I'll let you know.

CS

Well, that sounds pretty good so far.

I'm going to ask a potentially premature question: Shouldn't the turn signals on the trailer (KI) also flash simultaneously with the turn signals on the car, if a trailer is attached and I'm using the turn signals normally to the right or left? Because they're not doing that right now!
Otherwise, I look forward to your reply and thank you in advance.

Best, Sascha.

So, here I am again.
You need to connect chamber 4 at the hazard light switch to a chamber on the blue connector (32-pin) at the instrument cluster.
It varies depending on the year of manufacture.
- Until April 1998, this is Chamber 16.
- Room 4, starting May 1998.

I contacted Volkswagen at the time and obtained a suitable connector with a piece of cable attached from them.

Okay, you need to cut and insulate the wire that activates the instrument lighting on the WBS.

I have sent you a PDF of the wiring diagram for the AHK (trailer hitch) as a private message.

CS