Towbar wiring

[Diago]

Hey all! I'm looking to wire my towbar electrics into the car, using the existing main power supply wire which is fastened up behind the glovebox. I have found the wire ok, but upon checking to see if there was voltage from the wire, I find that there is no live feed. Is there a fuse or something which needs fitting into the fusebox in the engine bay, in order to power up this wire? Any guidance will be greatly appreciated.

[wullie480]

Originally Posted by Diago

Hey all! I'm looking to wire my towbar electrics into the car, using the existing main power supply wire which is fastened up behind the glovebox. I have found the wire ok, but upon checking to see if there was voltage from the wire, I find that there is no live feed. Is there a fuse or something which needs fitting into the fusebox in the engine bay, in order to power up this wire? Any guidance will be greatly appreciated.

You’ll find that the wire isn’t connected at the fuse box end underneath the bonnet.

[macafee2]

What will you be towing, trailer or caravan as you will need slightly different wiring

macafee2

[Diago]

Originally Posted by wullie480

You’ll find that the wire isn’t connected at the fuse box end underneath the bonnet.

Ah, thank you! That sounds possible, as I saw there were some spare fuse slots, but thought I'd ask around before I started pulling the fusebox apart. But I'll take a look underneath it and see what needs connecting up.

[Diago]

Originally Posted by macafee2

What will you be towing, trailer or caravan as you will need slightly different wiring

macafee2

Hi there! I'm converting it to a 13 pin socket, so that I can tow a caravan with twin electrics. I found the existing wiring to be in a bit of a shocking condition. So I' going to take it all out and start a fresh with it, and plan on wiring it to the power feed behind the glovebox, to make it a proper job. Rather than it being tacked into wires from the passenger compartment fusebox!

[COLVERT]

I ran a wire with an in-line fuse straight under the car from the battery. Very easy to do and so much faster and quicker than messing about with wiring inside the car.

Took all of 15 minutes including a small drilled hole in the spare wheel well for wiring access.----

[Diago]

Originally Posted by COLVERT

I ran a wire with an in-line fuse straight under the car from the battery. Very easy to do and so much faster and quicker than messing about with wiring inside the car.

Took all of 15 minutes including a small drilled hole in the spare wheel well for wiring access.----

Ah, that would be a plan, and sounds easier then fiddling about with fusebox wiring. I'll certainly consider doing that, but just really interested now as to what powers up that wire! haha

[HarryM1BYT]

Originally Posted by Diago

Ah, that would be a plan, and sounds easier then fiddling about with fusebox wiring. I'll certainly consider doing that, but just really interested now as to what powers up that wire! haha

The +ve feed from front to rear, is normally on all the time, but obviously must be fused. The other end of the glove box wire, will be curled up under the engine fuse panel, the panel just hinges up after undoing a bolt.

To charge a battery + run a fridge + supply lighting - that front to rear feed cable needs to be quite substantial, to avoid volts drop under load.

To switch that live feed to the fridge + trailer battery charge, the usual way is via a split charge relay. Modern split charge relays are voltage sensing type and usually mounted in the boot, near the socket.

[alanaslan]

Originally Posted by Diago

Hey all! I'm looking to wire my towbar electrics into the car, using the existing main power supply wire which is fastened up behind the glovebox. I have found the wire ok, but upon checking to see if there was voltage from the wire, I find that there is no live feed. Is there a fuse or something which needs fitting into the fusebox in the engine bay, in order to power up this wire? Any guidance will be greatly appreciated.

Hi thought I would share my October Caravan problem. I do most of the Towing with the tourer it had twin 7 pin sockets. Lighting wired off the offside tail light. Power had been run from the Battery to the rear of the car on a 4mm cable for the auxiliary socket. Both were picking up their negative return from a mounting point in the rear off side cubby.
Sadly on the way home from site at the end of October the bungee strap that was holding up the cables as the van is new and is thirteen pin and was connected to the car by a twin 7 to 13 adaptor.
Yes you all have guessed it the bungee failed and the cable from the van started rubbing on the road. Net result lots of shorts. And the earth or negative return cables to the body were fried.

My solution was to run a pair of 6 mm cables from the battery through an in line fuse to a pair of four way fuse boxes under the steering column. Relay packs gave me one as permanently live and one as switched live. One of the fused outputs from each fuse box running to the rear off side cubby on 4mm and 6mm cable to another pair of four way blade fuse fuse boxes.
I bought a full set of prewired towing sockets a pair of 7 way and one thirteen way. I ran a pair 6mm neutral return or earth cables to a solid connector bar each of the neutral cables I fused at fifty amps.
From the solid connector bar I ran inline fused cables to multi way relay packs and to the towing sockets negative cables.
The two seven pin units were straight forward. The thirteen pin socket was a nightmare.
I could not get a thirteen pin socket prewired with more than 8 core cable. So lights but no Caravan power.
Tried to buy either twelve or thirteen core cable that had a mixture of conductors as the lighting needed to vary from 1mm to 0.75mm depending on the circuit. With power supply and earth returns of 1.5mm and 2.5mm as required to charge the leisure battery and fridge then the tell tail and aux negative return.
I ended up having to go to Swift Caravans for the cable to wire up the thirteen core socket as no where else supplied the correct gauge of internal cables.
Very strange lots of suppliers sell 0.5mm twelve core 0.75mm twelve core and 1.0mm twelve core. But nobody other than the Caravan makers could supply the correct thirteen core cable.
As an old engineer I found this very strange.
No matter ten days ago I finished wiring up the three sockets on the back of the car. All done through multi relay packs fused both poles with the correct size of conductors in the multi core cables. Even have the caravans reversing camera connected up to a wireless broadcaster displaying on the cars android head unit.
A much bigger task than I had expected and a right eye opener on the incorrect cable used in prewired towing sockets.
I suspect the problem with the cables is just due to those who produce these things, not understanding the size of conductor required to carry the current the end use item may be drawing down the conductor.
My reason for fusing both poles was the damage that had occurred to the wiring that had been installed by whoever fitted the original twin seven pin sockets to the car.
If there is interest out there I will do my best to supply detailed information on how I have wired the cars towing sockets and why I have done it in the way I have. I will also try to supply part numbers of the equipment I have used.
Sorry to have hijacked your post but felt the information relevant as most people would just buy the off the shelf cables which are sadly not up to doing the job in a safe manor.
The Caravan must comply IEE regs seventeenth edition but the towing vehicle is not bound under these regulations. And seems to be an area exploited by those that supply the materials for the cars side of the wiring.
Alan


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[HarryM1BYT]

Only the mains (240v) part of the caravans wiring comes under the IEE Regs, but not any of the 12v wiring at all. I agree with your comments about core sizes of the multicore flexibles. There should be some the cores which are around 2.5mm, at least two, one for battery charging and for the fridge. I know mine is, but it is just the cable used for the 7 pin socket. I'm not surprised the cable colours and core sizes are only available from caravan specialists, the use is rather restricted.

I would suggest your 50amp is larger than needed, I made up a fuse for 30amp as the main supply fuse. That for the all of the caravans road lights + fridge + charging. I further split that 30amp supply at the rear into three at the back of the car, into 10amp road lights, 20amp fridge, 20amp battery charge. So a fault on one circuit, would not take everything out.