Towbar fitting

Oct 10, 2011
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Hi. Has anybody had problems with car battery drain after having a Towbar fitted. Having to charge my car battery every couple of days after getting my towbar fitted. I was wondering if there’s any easy way to disconnect towbar wiring to see if this is the cause or purely coincidental. The battery appears to be in good condition - cars only done 1000 miles. Current situation means towbar fitters are closed for the time being - they are willing to check electrics when they reopen. It’s a bypass wiring kit - I’m assuming it’s somehow connected to the battery and that may be a point to disconnect.
 
Jan 19, 2002
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If you google '13 pin socket wiring' you get colour coded diagrams of the pin uses. The live feeds are 9 (fused) and 10 (for fridge and battery) ignition controlled, and pin 13 is the earth for these. 9 -orange, 10 grey and 13 red/white. Might be worth checking that there are no stray wires etc, as none should be draining the battery when the 'van is not connected - and the relay should prevent this when the 'van is connected but the engine is not running.
 
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Thanks. Live feeds at socket seem ok and resistance at earth terminals is low suggesting good earthing. Still suspicious that problem occurred right after towbar fitting. Just not sure if there’s any easy way to disconnect towbar electrics to show for sure if drain is related to fitting or just coincidental.
 
Nov 11, 2009
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Thanks. Live feeds at socket seem ok and resistance at earth terminals is low suggesting good earthing. Still suspicious that problem occurred right after towbar fitting. Just not sure if there’s any easy way to disconnect towbar electrics to show for sure if drain is related to fitting or just coincidental.
Is there a fuse in the feed near your cars battery or did the towbar kit pick up “plug and play” points already installed at the rear of the car.
I know it’s wisdom of hindsight but always specify a car specific wiring kit. All major makers of towbars will supply a car specific option, or your installer will obtain one.
 
Oct 17, 2010
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There will be a something like a 25/30 amp fuse on the positive feed as near to the battery as possible, pull this will diconnect the power to the relay'
 
Oct 17, 2010
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Is there a fuse in the feed near your cars battery or did the towbar kit pick up “plug and play” points already installed at the rear of the car.
I know it’s wisdom of hindsight but always specify a car specific wiring kit. All major makers of towbars will supply a car specific option, or your installer will obtain one.
I have one on my motor. You know the most annoying the about bypass is the Buzzer, which I had to ask Swmbo if it was going on the motorway, couldn't hear it. Specific uses the car sytems/warning light no buzzer.
 
Oct 10, 2011
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Is there a fuse in the feed near your cars battery or did the towbar kit pick up “plug and play” points already installed at the rear of the car.
I know it’s wisdom of hindsight but always specify a car specific wiring kit. All major makers of towbars will supply a car specific option, or your installer will obtain one.



Not sure how it was fitted. The installer was recommended by the car dealer at point of sale and is a respected nationwide fitter. Tried pulling a 15a fuse in the glove box which looked like an addition but that made no difference to the parasitic drain on the battery.
 
Oct 10, 2011
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There will be a something like a 25/30 amp fuse on the positive feed as near to the battery as possible, pull this will diconnect the power to the relay'
Thanks. That sounds like what I’m looking for just to prove if it’s towbar or vehicle related problem.
 
Jun 20, 2005
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Not sure what car you have but clearly very new. The bypass kit is a means of controlling the caravans road lights via the vehicles own lighting system , without overloading the vehicle wiring. My best guess is that one of the relays fitted by the specialist is faulty. It may be shorting internally sending current to earth but maybe not enough to blow a fuse. Setting up modern cars requires a lot of IT knowledge. My fitter spent a long time showing me how all the tow electrics were phased and linked into the vehicles ECU. There is no buzzer to tell me the caravan indicators are working. Apparently if a bulb fails a warning comes up on the dashboard screen! Way beyond me. Hopefully the guy who installed it will be able to help you once the lockdown relaxes. Finally let me reassure you we are a very friendly bunch on here and are always willing to help a fellow caravanner even we don’t always get the right answer.
 
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Parksy

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Nov 12, 2009
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I've deleted several posts surrounding a silly disagreement that seems to have erupted from nowhere.
If I'd been monitoring the forum earlier I'd have nipped it in the bud, but having taken my eye briefly eye off the ball to sort out domestic duties things continued.
I'm back now and will take stronger action if these arguments continue.
 
Oct 10, 2011
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Not sure what car you have but clearly very new. The bypass kit is a means of controlling the caravans road lights via the vehicles own lighting system , without overloading the vehicle wiring. My best guess is that one of the relays fitted by the specialist is faulty. It may be shorting internally sending current to earth but maybe not enough to blow a fuse. Setting up modern cars requires a lot of IT knowledge. My fitter spent a long time showing me how all the tow electrics were phased and linked into the vehicles ECU. There is no buzzer to tell me the caravan indicators are working. Apparently if a bulb fails a warning comes up on the dashboard screen! Way beyond me. Hopefully the guy who installed it will be able to help you once the lockdown relaxes. Finally let me reassure you we are a very friendly bunch on here and are always willing to help a fellow caravanner even we don’t always get the right answer.
Thanks for the response. Makes sense and hopefully is the answer - just need to keep charging the battery for the time being and hope that no harm is done. Towbar was fitted by a reputable national chain who do a lot of kit for main dealers. I have however during my fault finding -( albeit with limited knowledge! ) - pulled out the fitted 15a fuse which was added to the fuse box. This results in zero voltage through pin 9 which previously was the same voltage as the battery when the new 15 a fuse was in place.
When the fuse is pulled and no power appears to be going to the socket I still have a drain on the battery.
I guess what I’m asking is can the cause of the battery drain still be towbar electrics when I have effectively broke the circuit by removing the fuse? I’d love for somebody to say yes so I can hopefully get a quick fix from towbar installers rather than for it to be an issue with the car and have to go through a Volkswagen dealer again. Had the car since the start of he year and my only journeys have been backwards and forwards to the dealership !
Cheers.
 

Damian

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Mar 14, 2005
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There will always be a drain on the battery from things like the alarm and radio memory.
The live pin 9 , as long as the van is not connected should not draw any power, its just an extension from the battery.

As has been said, modern cars are very sensitive as far as electrics are concerned and need things like the ECU programming when installing towbar electrics.
 
Oct 8, 2006
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If there was no issue with battery depletion before the towbar was fitted then it logically follows that it must be something to do with the towbar installation, but what?
What puzzles me - being a VW owner myself - is why the installer didn't use the VW kit. I've had two Passat Estates fitted Westfalia towbars with the VW wiring kit and, including reprogramming of the ECU, they charged me £540 inc VAT in 2015 and £600 inc VAT in 2018 - as against somewhere around a grand at a dealer. The disadvantage of not using the proper kit is that it doesn't communicate with the ECU so said box doesn't know you are towing. With the correct kit it will detect when something is hitched up and change the display on the Infotainment unit, it will activate the Trailer Stability Control system, and as Damien says it will show graphically on your LCD dashboard any light failures. For the record on most VWs if the ECU has been reprogrammed there will be a change in how the warning lights on the dash operate: normally the Traction Control light and ABS light go out simultaneously, but if a caravan is attached and plugged in one of the lights stays on for about 2 second longer than the other. Also engaging reverse gear which usually shows a graphic of the car and the parking sensors on the Infotainment unit will instead show a car with an A-frame on the rear of it.
 
Jun 20, 2005
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If there was no issue with battery depletion before the towbar was fitted then it logically follows that it must be something to do with the towbar installation, but what?
What puzzles me - being a VW owner myself - is why the installer didn't use the VW kit. I've had two Passat Estates fitted Westfalia towbars with the VW wiring kit and, including reprogramming of the ECU, they charged me £540 inc VAT in 2015 and £600 inc VAT in 2018 - as against somewhere around a grand at a dealer. The disadvantage of not using the proper kit is that it doesn't communicate with the ECU so said box doesn't know you are towing. With the correct kit it will detect when something is hitched up and change the display on the Infotainment unit, it will activate the Trailer Stability Control system, and as Damien says it will show graphically on your LCD dashboard any light failures. For the record on most VWs if the ECU has been reprogrammed there will be a change in how the warning lights on the dash operate: normally the Traction Control light and ABS light go out simultaneously, but if a caravan is attached and plugged in one of the lights stays on for about 2 second longer than the other. Also engaging reverse gear which usually shows a graphic of the car and the parking sensors on the Infotainment unit will instead show a car with an A-frame on the rear of it.
Mines a VW too. My chap spent twenty minutes or so showing me his laptop connected to the cars computer that the Westphalia and wiring harness etc were doing what they had to . The displays on screen in the car were mind blowing for a dinosaur like me!
 
Oct 10, 2011
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If there was no issue with battery depletion before the towbar was fitted then it logically follows that it must be something to do with the towbar installation, but what?
What puzzles me - being a VW owner myself - is why the installer didn't use the VW kit. I've had two Passat Estates fitted Westfalia towbars with the VW wiring kit and, including reprogramming of the ECU, they charged me £540 inc VAT in 2015 and £600 inc VAT in 2018 - as against somewhere around a grand at a dealer. The disadvantage of not using the proper kit is that it doesn't communicate with the ECU so said box doesn't know you are towing. With the correct kit it will detect when something is hitched up and change the display on the Infotainment unit, it will activate the Trailer Stability Control system, and as Damien says it will show graphically on your LCD dashboard any light failures. For the record on most VWs if the ECU has been reprogrammed there will be a change in how the warning lights on the dash operate: normally the Traction Control light and ABS light go out simultaneously, but if a caravan is attached and plugged in one of the lights stays on for about 2 second longer than the other. Also engaging reverse gear which usually shows a graphic of the car and the parking sensors on the Infotainment unit will instead show a car with an A-frame on the rear of it.
It’s a pre-reg Tiguan nd I was advised by the fitter that a detachable without vehicle specific electrics was my best option. In hindsight it was maybe just the easier fit for himself. The only advantage I could see from vehicle specific was stability control but as an experienced caravaner who now only intends to go short journeys towing I went with his suggestion. The reason for detachable was to avoid possible issues with parking sensors. I do agree the logical explanation for problems is an issue with towbar electrics but can’t understand why I still have parasitic draw on the battery when I pull the fuse and effectively break the circuit. Not sure if it may just be coincidence and a faulty battery or one which has somehow deteriorated beyond use due to the car being pre-reg and being stored without moving for over a year without moving. As I’ve said I hope it is a simple fix at the towbar installers. Not found VW dealerships the most helpful so far! Thanks.
 
Jun 20, 2005
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I suspect the current draw is still from a faulty relay, the bypass one for the lights. Your Tiguan has day light running lights which may be sending a live signal to the relay? Just a thought.
 
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Oct 8, 2006
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If the fitter did connect up to the ECU he may have changed a wrong computer address (typo) and set something permanently active that you cannot see but nonetheless is drawing current.

One thing you can do is disconnect the battery overnight. That will make the ECU forget its optimum settings which it will re-learn as you drive. If the battery still goes down before you have driven then it has to be a programming error - or the battery is stuffed!
 
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Nov 16, 2015
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A thought, ! During times of car inactivity. If your car battey runs down below a certain voltage, will the automatic locking open , if locked. Or stay locked. It's probably dependant on type.

I did read a few years ago that if a car went into water and the battery shorted out the doors would unlock, for saftey reasons. Sensible.
 
Oct 8, 2006
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If the battery gets low the electric locking will not work - which is why VW supply you with a key that is buried in the fob and slides in under the (usually nearside) door handle. Opening the door will of course set off the alarm until the fob is detected and the ignition switched on.
 

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