Faulty towbar electrics? - Passat B5.5

[tdi_uk]

Hello, this is my first post on here.

My 2003 Passat Variant failed it's MOT as the single O/S rear foglight was no longer working. Despite there being power to both of the contacts in the light cluster when a 21w/4w bulb was fitted into the socket the power to the foglight would be cut off; the sidelights, etc. were unaffected. I checked for voltages where ever I could insert my meter's probes and also checked with a test lamp which, when put in the foglight circuit, would never light up under any circumstances. Whenever there was a bulb (a load?) in the foglight circuit the circuit would cut out.

The towbar electrics harness was dealer installed by the looks of it as it has VAG plugs and sockets which, I found out much later, could be disconnected to enable the original light cluster plug to be plugged into the light cluster socket. Once back to its pre-towbar electrics the foglight worked and I got my MOT!

So the fault appears to lie in the towbar electrics. Now with a bit searching on this site I've found that there are now '7 way bypass relays' and 'N-type sockets with foglight cutout' that turn off a car's foglight when towing. Could one of these be fitted and is causing the foglight to be cut out even when not towing? (I can't tell you what happens if I connect up a caravan/trailer as I don't have one at the moment).

The towing electrics harness fitted has a blue rectangular can with an 8 wire plug/socket and with these details:

Anhanger Blinkuberwaching
ETH 321106
2(4)x21W

Is this just a heavy duty flasher can?

Can anyone advise me what to look for in my quest to getting the foglight to work with the towbar electrics fitted?

Thanks

Ian (Not an electrician. I prefer the grubby bits!)

[martin1810]

I would take the towing socket apart and have a look. You may have a corroded wire that is earthing out or touching one of the other circuits. The loom to the socket may have rubbed on something and be shorting out. If you have a genuine towbar socket it may have a micro switch in it.

[David1953]

I had a volvo with a towbar plug that had a small black pin that was pushed in by the socket and disconnected the foglights but didn't release. Might be what it is David

[MagicMat]

I know this is an old thread, but im having this exact problem. Has anyone found a fix?

[tdi_uk]

As the OP, in my case, it was a corroded N-type socket. I replaced it with another with the fog light cutout.

[revvic]

Hope this helps to unravel the confusion when it comes to 12n towbar electrics,



There are 7 female conectors, 6 in a circle and 1 in the center
Top centre is pin 1, going clockwise takes you to pin 2 and so on till pin 6, the center is pin 7

pin.....colour..........purpose.................vw/audi 95 onwards wire/loom colours,
1.......yellow..........left turn................black/white
2.......blue.............fog light................grey/white
3.......white...........earth....................b rown
4.......green...........right turn..............green/black
5.......brown..........right tail................grey/red
6.......red..............brake light.............black/red
7.......black...........left tail..................grey/red
8.......purple..........foglight cutout........grey/white


With the original cutout issue try dousing the socket with wd40 and manipulating the cutout switch* at same time with something like a ear bud, this may save you having to open up the socket,
(*usualy a small plastic pin that gets pushed in when a 12n male conector is inserted)

If that doesnt work you have two options
1 open up socket, check all conections are secure and clean cutout conections and reassemble, but this relies on you having to remove towball or cut cable ties so you have enough slack to work with.

2 temperarily bypass the cutout to pass your mot,
all the wiring should be found hidden behind the offside interior panel,
to make a cutout curcuit the blue(2) and purple(8) are both connected to the cars grey/white foglight wire to make a paralel curcuit and then the original curcuit grey/white is cut leaving the blue connected to the switch end and the purple conected to the foglamp,
So by my reconing if you cut and insulate the purple wire of the 12n where it joins the grey/white leaving enough wire to reconect to later if you decide to fix cutout via option 1, then find grey/white conected to blue wire of the 12n and join to other grey/white restoring the foglight, and pin 2 will still work as designed minus cutout function

[MagicMat]

Thanks the info guys,

Very sorry to take so long replying.

So it sounds like a new tow electrics / circular plug thing? (Very technical)

Unless i can clean it with an ear bud. Or open it up and clean the back connections.

Other option is to make a cutout switch for the fog?

That about right??