We have just bought a second-hand 2017 Yeti 4x4 replacing our 2010 version.  This was not advertised as having a towbar. However, there was a detachable bar in the boot and it has dedicated wiring (VAG).

 

We have now checked the towbar electrics using our and caravan although they respond correctly - lights, indicators and recognition of the trailer when reversing, the repeater click was very fast when indicating left indicator and a message "Trailer check left turn signal" was displayed. I then tried a trailer light bar and again the lights worked but neither of the indicators worked and the same message (I have checked that the light bar works, using my Superb with non-dedicated towbar wiring.)

 

I ran a VCDS scan and the following errors were noted

 

These could both be reset when the caravan was disconnected and did not recur until either the caravan or my trailer lightbar was attached. 

 

I have booked the car to go to a local towbar fitter to be checked (both detachable towbar and the electrics).

 

Any thoughts regarding what the issue could be would be appreciated?  Could it be a Coding issue?

 

Many thanks 

Could be something simple, like a bad bulb or a bad earth.

Try replacing the bulb. Check the earth wire is secure as well inside the light fitting.

 

Not an LED bulb is it?

Door mirror turn signal units are expensive from VAG, in the region of £55 each - after a recent MOT fail for this reason I bought a cheapo pair off eBay for £20 with free postage which work perfectly well. 

Fitting involves removing the mirror glass to get to the mirror cover clips,  the 2 removal screws are then apparent - a ten minute job, max.   

Hi

 

The fact that you are getting fault indications for both tail lamps and indicators makes me suspicious that there is a bad (high resistance) common earth which is causing all or part of the current from one bulb to find its way "backwards" through another, rather than all going to earth.  Although this can make lamps dimmer than normal, it may not be immediately noticable to the naked eye.  However, the current monitoring circuits aren't so easily fooled and will complain due to the current being lower than the expected value.  The rapid flashing (synthesised these days) is to alert you because it "thinks" the low current is due to a failed indicator bulb.

 

I suggest you check the earth pin in the car socket (Pin 3 if it's a 13 Pin style) for tarnishing.

Many thanks to everyone who has responded.

 

I tried 2 additional trailers with similar results. What I also noted that when the indicators are on the caravan the side lights do not work on that side and if the indicators are put to the other side, the side light on that side goes off and works on the opposite side.

 

Although the left turn error code does return each time a trailer/caravan/lightbar is attached, the indicator in the left mirror continues to operate. Though it dd not work when I tested it using VCDS!

 

It is being seen by a well thought of local towbar fitter tomorrow. I will let you know how it goes. I would have liked to have checked the earth pin but the appointment has just been brought forward to 9am.

On 09/11/2022 at 16:58, Carlodiesel said:

Could be something simple, like a bad bulb or a bad earth.

Try replacing the bulb. Check the earth wire is secure as well inside the light fitting.

 

^^^^ Especially any earth connections.

The Yeti saw the towbar specialist. His diagnostics did not identify any issues! I did not manage to speak with the person who did the checking.

 

I checked it on 2 trailers, our caravan and a light bar. This time all lights and indicators worked except for the left sidelights on all but the Light bar where the right sidelights did not work.  A quick investigation identified that on the lightbar the side lights had been wired to the wrong side i.e. brown wire to the left sidelight. So at least i have a consistent issue with the Black wire (left sidelights).

 

Car booked in at specialist again, this time i am taking the light bar so that they can see the black wire (normally) left sidelight does not work.

 

 

 

Sounds like a specialist in avoiding getting his hands dirty.

 

The first thing I would have done would have been to pull forward the 7 pin (presumably) trailer socket and check the wiring connections for corrosion, wires pulled out etc.

 

Trailer sockets have the same connections and (lack of) water protection as they did 50 years ago and are very prone to failure, VCDS would have been my very last resort, using my eyes and common sense would have been the first.

 

I do also have a plug in tester because trying other lighting boards can introduce myriad other errors as you have found, there is only one thing more shonky than a trailer socket & plug and that is trailer light units!

 

I cant believe you have to have 2 appointments with a "specialist" to resolve such a basic issue.

Edited 11 November, 20223 yr by J.R.

14 hours ago, J.R. said:

Sounds like a specialist in avoiding getting his hands dirty.

 

The first thing I would have done would have been to pull forward the 7 pin (presumably) trailer socket and check the wiring connections for corrosion, wires pulled out etc.

 

Trailer sockets have the same connections and (lack of) water protection as they did 50 years ago and are very prone to failure, VCDS would have been my very last resort, using my eyes and common sense would have been the first.

 

I do also have a plug in tester because trying other lighting boards can introduce myriad other errors as you have found, there is only one thing more shonky than a trailer socket & plug and that is trailer light units!

 

I cant believe you have to have 2 appointments with a "specialist" to resolve such a basic issue.

Before seeing your message, I removed the 13-pin socket from the Yeti checked that no obvious loose wires (particularly Brown on 3) and just inserted and reinserted the light bar plug. On testing all good; no error messages on the maxidot. Same result on our horse trailer - Result.

 

I have cancelled the specialist. 

 

Thanks for all your suggestions, it appears it was probably mild corrosion as the tow bar has not been used for at least 6 months

 

 

1 hour ago, Smallholdertoo said:

I have cancelled the specialist. 

I'm glad to hear it, he had his chance to do what you have done.

 

Assuming that it was the same specialist.

My pal has a 13 pin socket which gets lots of use, he had a problem with it  when we picked up his new tractor from Belgium during the lockdown, we had stopped over at my place before he did the final 800km back to his home.

 

It had been a recurrent problem and was one of the pins not making contact properly in the socket, the solution was same as what I have done on 7 pin sockets, to spread the pin using a fine flat blade screwdriver in the slots and to ream out the female pins by hand with a drill bit.

 

For some reason I can't recall it was apparent that the 13 pin sockets were more vulnerable to this failure.

Switch and contact cleaner followed by a smear of vaseline works for me!!

I live by the sea so lots of salt / rain etc blowing about!!

37 minutes ago, J.R. said:

My pal has a 13 pin socket which gets lots of use, he had a problem with it  when we picked up his new tractor from Belgium during the lockdown, we had stopped over at my place before he did the final 800km back to his home.

 

It had been a recurrent problem and was one of the pins not making contact properly in the socket, the solution was same as what I have done on 7 pin sockets, to spread the pin using a fine flat blade screwdriver in the slots and to ream out the female pins by hand with a drill bit.

 

For some reason I can't recall it was apparent that the 13 pin sockets were more vulnerable to this failure.

From my recollection, back in the days I towed, there is actually a special hand tool available to clean both male and female trailer connector contacts. Perhaps a useful addition to toolbox?

As above..

For less than a fiver you could buy a "Hella Kleenaplug" (see eBay listing and probably available from other outlets),  a small tool that will clean out both male and female pins/sockets;  in my caravanning days there was one permanently parked in the car glove box in case of dodgy connections.

Edited 12 November, 20223 yr by Zarniwoop

3 hours ago, Zarniwoop said:

As above..

For less than a fiver you could buy a "Hella Kleenaplug" (see eBay listing and probably available from other outlets),  a small tool that will clean out both male and female pins/sockets;  in my caravanning days there was one permanently parked in the car glove box in case of dodgy connections.

Sounds a good idea, does it work for a 13-pin socket/plug or just 7-pin?

5 minutes ago, Smallholdertoo said:

Sounds a good idea, does it work for a 13-pin socket/plug or just 7-pin?

All pins and sockets - the item has individual tools for them - sort of like the little 4-way tool for tyre valve servicing.

Hi

 

The 7 pin trailer socket design goes back decades, and has the design weakness of only one shared earth pin for all the lights.  With the exposed location and the use of plain brass, its very common to get tarnishing and high resistance, and if this happens to the earth pin you get all sorts of odd interactions between the different lights.  Anyone calling themeselves a towbar electrics specialist should be more than familiar with this effect.

 

The newer 13 pin sockets seem to have carried over the idea of just one earth pin.  Whoever designed it clearly didn't own a trailer !

Ha, if its a french design, then it would have been done after a very good friday lunch, ie a friday afternoon job!!   😄

Funny isn't it, but I used to have to clean the old 7 pin plugs at the start of every season and atleast once more durimg the summer, but now with the 13 pin plug I very rarely have to do anything. It just works!
All I do is give it a spray of silicone grease when I put the 'van away for the winter.