Electrical problems with VW Golf V towbar

[JandG]

Hi,
Almost 2 months ago I had an original VW towbar fitted to my 2005 Golf V with the VW wiring harness.
Then I bought a brandnew aussie made box trailer.
Since then I am encountering the following problem:
1. When I hit the brakes the trailer brake lights come on ok.
2. When I use left or right blinker the trailer blinker works ok
3. When I turn on the normal lights the trailer rear lights come on

Now...........where is the problem I hear you say.............well:

All the above 1, 2, 3 work ok when used one at the time.

However when the normal lights are turned on in combination with either the brake lights or a blinker then a fault light on the dash comes on indicating a light bulb failure.

I have been back to the VW dealer twice now and they seem to be unable to fix. They replaced the cable loom and "module???) but still no good.

Because the Golf monitors each light bulb including the ones on the trailer there is some kind of current sensing (continuity) involved.

(In other words if I take the trailer left blinker light out that will show on the dash with a message + the dash light bulb failure light will come on. That side seems all ok)


If VW is not able to fix this would I be entitled for a refund plus replacement of the rear bumper? (because they had to cut a hole in it)

Hope they can fix it though although I am very disappointed seeing the cost of the whole excersise was $1,540.00. They don't even have a test facility to simulate the trailer so that I have to bring my trailer every time.

BTW I have hooked up my trailer to a Holden Caprice in the neighbourhood here and my trailer seems 100% ok. I have also hooked up another trailer to my Golf and it's giving the same fault indication as described above.

One thing I did notice is that the Golf does not have 2 filament light bulbs for rear and brake light. They use a 12V/21W single filament for both rear light and brake light. Checking with a multimeter I found that the voltage on the Golf rear light bulb (single filament) changes to get the normal rear light brightness and the brake light brightness. They could be using pulses to increase average voltage thereby changing brightness, I haven't checked this yet but will put my Oscilloscope on it to verify.

The trailer ofcourse has the normal double filament like 12V/5W and 12V/21W combined light bulb. Maybe this has got something to do with it.

Anyone got any suggestions.

Waiting for the VW dealer now to see what the next step is going to be.

[brackie]

Hi,
The trailer ofcourse has the normal double filament like 12V/5W and 12V/21W combined light bulb. Maybe this has got something to do with it.

Anyone got any suggestions.

Waiting for the VW dealer now to see what the next step is going to be.
I would say that's the answer. Have you tried replacing the double filament bulb and holder with a 12V/21W single filament setup?

[syncro]

Sounds like an earth problem.
The trailer is probably earthed to frame and the towbar is not.
(or the other way around)
It is very easy to make up a test plug for the car.
Where are you?

[JandG]

Sounds like an earth problem.
The trailer is probably earthed to frame and the towbar is not.
(or the other way around)
It is very easy to make up a test plug for the car.
Where are you?

Thanks for the replies.
I am in Sydney.

I can't see why I should have to replace the light fittings on my new Australian made trailer with no guarantee that that will work. Volkswagen sells in in Aus and it has to be fit for purpose.
That is why I went original parts in order not to have any problems.

Tell me about the test plug, may be I can make myself?

Thanks heaps

[JandG]

I would say that's the answer. Have you tried replacing the double filament bulb and holder with a 12V/21W single filament setup?

Can't do that I would think. The VW adaptor cable also has separate wires for brake and rear light. In other words it is made for the standard here with a 7 pin straight plug.

Thanks for your reply anyway

[Golf Loon]

Are the bulbs in the trailer exactly the same on both sides. Same make and wattage? I used to have a Jaguar XJ6 and if the bulbs were not identical, you got the same fault. Even bulbs of different brands had different resistances. Hope you get it sorted.

[JandG]

Are the bulbs in the trailer exactly the same on both sides. Same make and wattage? I used to have a Jaguar XJ6 and if the bulbs were not identical, you got the same fault. Even bulbs of different brands had different resistances. Hope you get it sorted.



Good advise there thank you. I am about to go and check a few things myself.

Will report any findings so that it may help others.
Cheers

[syncro]

Dual filaments wont make any difference.
Where in Sydney are you?

[JandG]

Dual filaments wont make any difference.
Where in Sydney are you?


I will travel anywhere in Sydney to get this sorted.

I am actually in the Windsor/Richmond area.

JandG

[syncro]

I'm at Picnic Point near the M5 toll plaza.
If you want to work out a time and bring the trailer over.
I work shifts and am usually home mornings.
email me at; plander@optusnet.com.au

Phill

[JandG]

I'm at Picnic Point near the M5 toll plaza.
If you want to work out a time and bring the trailer over.
I work shifts and am usually home mornings.
email me at; plander@optusnet.com.au

Phill



Email sent.

[syncro]

Has anyone else here with a Golf 5 (or other can-bus car) had this problem?

It looks like UK and Euro trailer wiring has a seperate circuit for left and right tail lights and that's were the problem lies. To overcome this the VW 13 pin round Euro to flat 7 pin Australia adapter has two diodes to join the two tail lights together which causes problems with the bulb check function.

I wonder if there is an Australian software upgrade to rectify this:confused:

[JandG]

Been back to VW dealer several times now to sort this out. Went yesterday after they had told me they now have a "test box" to plug into the 7 pin plug to see if there are any problems. Guess what. It was bringing up the same fault as when I plug in my trailer plug.

Now they want the car for at least 2-3 days and will get in contact with VW to sort it out.

Can't believe what a drama this has been. At least they are convinced now that it is not my trailer causing it. Will post results after mid February when they have had the car. Have to say they are persistant and want to know what the problem is.
Gonna get a loan car. Hope it's a GTI!

Cheers

[MultiplexMan]

Hi JandG,

Did you get the tow bar sorted?

I am considering the towbar for my GTI but won't spend the money if the OEM kit has "issues".

Cheers,
MM

[njg02]

G'day guys.

I had the same issue a couple of months ago. Three trailers and one would not work on the golf. Everything worked on the T5. Auto electrician was at a loss and the local dealer pulled everything apart and changed modules and eventually found an earth problem. Check the earth if you havn't already.

Neil

[syncro]

The problem is that the VW wiring is not compatible with Australian trailers.

In Europe they have a left and right tail light circuit. In Australia they just have a tail light circuit.

[homie100968]

The problem is that the VW wiring is not compatible with Australian trailers.

In Europe they have a left and right tail light circuit. In Australia they just have a tail light circuit.

:)

I have exactly the same problem as everyone else here...

Im an electrician and ill be ripping the whole car to bits if the dealership can't find a workable solution.
Ive been thinking about building a box with some high power transistors to switch the lights on and off .. which would isolate the trailer from the cars std wiring loom and "should" stop the idiot light telling me i got problems.
If this works it will mean the trailer lighting system wont cause the idiot light to iluminate even if the trailer has problems. But I dont have globes in mine anyhow.. All LED indicators etc... and all sealed so no water ingress to play havoc with earthing etc.
If I get this system up and running Ill let you know.. if not ill be buying a european loom to do it!

[LiFers]

In Europe they have a left and right tail light circuit. In Australia they just have a tail light circuit.

This would be to cater for americans where brake lights are also blinkers.

[homie100968]

:)

I have exactly the same problem as everyone else here...

Im an electrician and ill be ripping the whole car to bits if the dealership can't find a workable solution.
Ive been thinking about building a box with some high power transistors to switch the lights on and off .. which would isolate the trailer from the cars std wiring loom and "should" stop the idiot light telling me i got problems.
If this works it will mean the trailer lighting system wont cause the idiot light to iluminate even if the trailer has problems. But I dont have globes in mine anyhow.. All LED indicators etc... and all sealed so no water ingress to play havoc with earthing etc.
If I get this system up and running Ill let you know.. if not ill be buying a european loom to do it!

ok so here goes...06Nov07
I pulled the right rear indicator assembly free from the vehicle and removed the globe carrier and then plugged it in to the wiring D connector..
tested for dc voltage and nothing.... tested for ac voltage and hey presto.. 5v ac ( @ 100Hz ) .. the indicator and parker (the inside globe) are both single use.. the outer globe is dual use .. but only 1 fillament... so its pulsed 5V ac to work as a parker and then (10-12V ? its brighter so must be higher voltage) V ac for brake light duties... so .... im guessing a smart relay will have to be employed to be able to get around the dual voltage tail / brake light .. im figuring on buying one from england and trying it out .. see what it can do.. all the other globes arent a problem... just that 1 brake / tail combo...

[homie100968]

ok so here goes...06Nov07
I pulled the right rear indicator assembly free from the vehicle and removed the globe carrier and then plugged it in to the wiring D connector..
tested for dc voltage and nothing.... tested for ac voltage and hey presto.. 5v ac ( @ 100Hz ) .. the indicator and parker (the inside globe) are both single use.. the outer globe is dual use .. but only 1 fillament... so its pulsed 5V ac to work as a parker and then (10-12V ? its brighter so must be higher voltage) V ac for brake light duties... so .... im guessing a smart relay will have to be employed to be able to get around the dual voltage tail / brake light .. im figuring on buying one from england and trying it out .. see what it can do.. all the other globes arent a problem... just that 1 brake / tail combo...

Ok some more of the same..
Ive now found out the multimeter im using isnt reading the dc voltage because its pulsed !! hence the statement of having AC voltage..
Dc pulsed to the lights to change intensity of the globe.. hence being able to use a single fillament globe to get both park and stop on the one globe!!
my box of tricks is held up due to it costing more to ship than what the unit costs..!! So... I have been working on an alternative .. Im planing to try a voltage sensitive relay from Jaycar electronics to see if it can be employed to switch on for the brake lights.. Ill keep you posted.

[motootto]

I know these relate to A3s but some of the theory should be the same.
I noticed that they use the centre stop light for the brake lights as this is single use.
This one is about wiring for the towbar
http://oooo-a3.blogspot.com/2006/10/trailer-light-wiring.html
and this one is about designing and installing a towbar
http://oooo-a3.blogspot.com/2006/11/custom-trailer-hitch.html

[BarneyBoy]

Dunno whether this applies to you, but also if you have parking sensors fitted, you have to tell the system that you have a trailer hooked up. This is normally done in the car's software, and stops the parking system from freaking out when you select reverse with the trailer attached.

If the dealer has fitted the towbar and not told the car about it, you could have some issues. It's also one of the reasons why the Mk5 bar is so expensive compared to regular bars (in addition, the multiplex wiring is a more complex beast to deal with). There are also (according to my dealer - maybe NOT Gospel ;-)) issues with headlight levelling and towing that may occur, particularly if bi-xenons are fitted too.

Anyhow, maybe (like with a doctor) you should seek a second opinion. Could be that the guy at your dealership has never fitted a towbar before (it's been known to happen you know j: )

(Edit) BTW, you may be interested to know that a rear valence especially for towbars exists for all the various valences (stock, GT, GTI). It has a removable cover for the tongue to stick through. Saw it in the parts book while struggling with a VW parts guy.

[jose_288]

You can install a module to insolate the electrical system towbar. Exist universal modules to allow the check-control and multiplexed systems with PWM signal by one wire (brake/tail) or (fog/tail).
You can see FAQ's in http://http://www.zitronik.com

[saabman]

Hi Jose_288 that link to zitronik is a no goer :(
Has anyone obtained an aftermarket converter for the trailer lights?