I have recently changed my tow car and I now have a VW Passat 2012 B7 variant,upon enquiring about a tow bar and electrics I was advised I would need a dedicated wiring loom rather than a standard loom that is scotch locked in to the car`s wiring.The cost of this dedicated loom is a staggering £220 which is half of the cost of the job in total.I appreciate modern cars are very technical these days but this seems astronomical.Does any one have any experience of this or can offer any advice,thanks.
Tow car electrics
- Thread starter Burn
- Start date
Hello Burn,
Modern cars are very technical, and many items of electrical equipment are controlled by a system called CanBus. I don't know the detailed aspects of this but I understand that central computers control most items and they also monitor voltages and currents, so the system can detect things like blown bulbs, or other items that might go out of range.
Tacking on additional loads such a bulbs on monitored lines using scotch locks might well cause the systems to flag up errors. Using the correct loom will ensure the new loads are applied at the correct points of the cars loom, and in some cases the cars CPU has to be updated to alert it to the changes.
Using incorrect wiring harnesses might invalidate any warranty thats left on the car.
Modern cars are very technical, and many items of electrical equipment are controlled by a system called CanBus. I don't know the detailed aspects of this but I understand that central computers control most items and they also monitor voltages and currents, so the system can detect things like blown bulbs, or other items that might go out of range.
Tacking on additional loads such a bulbs on monitored lines using scotch locks might well cause the systems to flag up errors. Using the correct loom will ensure the new loads are applied at the correct points of the cars loom, and in some cases the cars CPU has to be updated to alert it to the changes.
Using incorrect wiring harnesses might invalidate any warranty thats left on the car.
Burn,
When I bought a Passat B7 in September 2011 VW did not have a wiring loom available because of a quality issue and so my dealer arranged for me to have an after market tow bar and wiring loom fitted by the local Indespension branch.
They fitted a PCT removable tow bar and a proprietary wiring loom to pick up on the CAN bus. The dealer then programmed the car to recognise this so the rear parking sensors were switched off when the caravan was connected to the car and the car alarm sounded if somebody unplugged the caravan electrics whilst it was connected to the locked car.
If my memory is correct the total cost was in the region of £650 but it was worth it for the quality of the product and the fact that no visible bumper cuts were made.
regards
Firkle
When I bought a Passat B7 in September 2011 VW did not have a wiring loom available because of a quality issue and so my dealer arranged for me to have an after market tow bar and wiring loom fitted by the local Indespension branch.
They fitted a PCT removable tow bar and a proprietary wiring loom to pick up on the CAN bus. The dealer then programmed the car to recognise this so the rear parking sensors were switched off when the caravan was connected to the car and the car alarm sounded if somebody unplugged the caravan electrics whilst it was connected to the locked car.
If my memory is correct the total cost was in the region of £650 but it was worth it for the quality of the product and the fact that no visible bumper cuts were made.
regards
Firkle
Thanks for the reply and I can understand the issues with modern cars etc but £220,really,have seen pictures and it`s just wires and push fit block connectors.
As others have said, it really is a must to have the correct connection. The £220 is not just connections to lighting wires: it will have a software interface associated with it so that it can talk to the car control system. It also means that the towing programme can be activated in the control system which I understand greatly improves towing safety (never had to try it yet- thankfully.)
We have a s/h Passat B6 estate (58 plate) and the dealer had his regular contractor fit a bar. I had asked for Westphalia but they fitted a Thule with removable ball. I understand the bar came complete with interface and the electrics were just plug in. Note also that it (as most new bars will be) can with 13-pin a connector.
The problem is that if you do not have the correct interface fitted (a) it may invalidate any warranty you have and (b) if something goes wrong it could cause the car to stop and refuse to continue.
CAN-Bus was mentioned. This is now pretty well the standard wiring configuration in most modern cars albeit some have proprietry versions.
In earlier cars all electrical functions started at the front. If you put you foot on the brake a pressure switch supplied power to cables that ran from the front to the back of the car to light the stop lamps. Every rear light (sometimes pairs) had to have its own cable, which meant bulky and heavy cable looms using a lot of copper. Manufacturers were under pressure to reduce emissions and one way to do that is to reduce weight, so they invented CAN-Bus.
Instead of having individual wires, there is one quite thick power wire going round the car to everywhere it is needed. Accompanying it is a signalling wire. Now when you put you foot on the brake the pressure switch monitor sends a message down the signal wire to the control system which in turns sends a message to an interface at the rear of the car. This message tells it to apply power to the brake lights - which it does. When you take your foot off the brake pedal another set of signals flows around to tell the rear interface to switch the lights off. The interface at the back often periodically puts a small current through the lights to ensure the bulbs are still good. It would expect to see the effect of the caravan lights in addition to the car lights because when you hitched up the control system would have recognised such and told each of the appropriate lighting interfaces - by a message down the signalling cable - to expect extra load, thus if a bulb on the caravan fails you should get a warning. This sort of modus operandi means that a computer can be connected to the car not only to monitor what is going on but to initiate and test switching functions.
We have a s/h Passat B6 estate (58 plate) and the dealer had his regular contractor fit a bar. I had asked for Westphalia but they fitted a Thule with removable ball. I understand the bar came complete with interface and the electrics were just plug in. Note also that it (as most new bars will be) can with 13-pin a connector.
The problem is that if you do not have the correct interface fitted (a) it may invalidate any warranty you have and (b) if something goes wrong it could cause the car to stop and refuse to continue.
CAN-Bus was mentioned. This is now pretty well the standard wiring configuration in most modern cars albeit some have proprietry versions.
In earlier cars all electrical functions started at the front. If you put you foot on the brake a pressure switch supplied power to cables that ran from the front to the back of the car to light the stop lamps. Every rear light (sometimes pairs) had to have its own cable, which meant bulky and heavy cable looms using a lot of copper. Manufacturers were under pressure to reduce emissions and one way to do that is to reduce weight, so they invented CAN-Bus.
Instead of having individual wires, there is one quite thick power wire going round the car to everywhere it is needed. Accompanying it is a signalling wire. Now when you put you foot on the brake the pressure switch monitor sends a message down the signal wire to the control system which in turns sends a message to an interface at the rear of the car. This message tells it to apply power to the brake lights - which it does. When you take your foot off the brake pedal another set of signals flows around to tell the rear interface to switch the lights off. The interface at the back often periodically puts a small current through the lights to ensure the bulbs are still good. It would expect to see the effect of the caravan lights in addition to the car lights because when you hitched up the control system would have recognised such and told each of the appropriate lighting interfaces - by a message down the signalling cable - to expect extra load, thus if a bulb on the caravan fails you should get a warning. This sort of modus operandi means that a computer can be connected to the car not only to monitor what is going on but to initiate and test switching functions.
You don't have to have a dedicated harness with a can bus system, my Mazda has only the bypass system, with scotch locks.
However if you have a car trailer program it won't work, so you need to make enquires with a towbar fitter who can advise.
Many people are frightened into going the VS route due to scare stories.
My car has no bulb failure system or TS, so I only have the rear sensors that operate in reverse, I just push a dash board switch to turn them off.
I might add that the VS (vehicle specific) harness doesn't always cater for the permanent and fridge supplies, so extra cables are run for these often from the battery.
Give this company a ring. Some information on the bottom of this link.
http://www.pfjones.co.uk/tow-bar-electrics.html
However if you have a car trailer program it won't work, so you need to make enquires with a towbar fitter who can advise.
Many people are frightened into going the VS route due to scare stories.
My car has no bulb failure system or TS, so I only have the rear sensors that operate in reverse, I just push a dash board switch to turn them off.
I might add that the VS (vehicle specific) harness doesn't always cater for the permanent and fridge supplies, so extra cables are run for these often from the battery.
Give this company a ring. Some information on the bottom of this link.
http://www.pfjones.co.uk/tow-bar-electrics.html
Thank you to all replies on this,i am more informed and understanding of the cost and was beginning to think it was another example of being ripped off.Xtrailman,i will have a look around that w/site and call them for a definite quote.
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