Towbar wiring

[sikelsh]

When Harry & Son did mine, I bought this

http://www.towsure.com/product/Smart_7_Way_CanBus_Relay

Used this Image



And then used this info that is specific to the car

Left indicator = Green + Pink

Right indicator = Green + Grey

Brake light = Green + Blue

Left sidelight = Red + Grey

Right sidelight = Red + Blue

Fog light = Blue + Yellow

Reverse light = Brown + Green

Ran a feed from the fusebox and installed a 25 Amp fuse at the relay box.

The right indicator and sidelight were run across the boot as well.

Worked a dream ever since

The above will give you Single Electrics, and its not plug and play.

Simon

[Graham E]

Thanks that's very helpful.

[HarryM1BYT]

Originally Posted by sikelsh

When Harry & Son did mine, I bought this

http://www.towsure.com/product/Smart_7_Way_CanBus_Relay

Used this Image



And then used this info that is specific to the car

Left indicator = Green + Pink

Right indicator = Green + Grey

Brake light = Green + Blue

Left sidelight = Red + Grey

Right sidelight = Red + Blue

Fog light = Blue + Yellow

Reverse light = Brown + Green

Ran a feed from the fusebox and installed a 25 Amp fuse at the relay box.

The right indicator and sidelight were run across the boot as well.

Worked a dream ever since

The above will give you Single Electrics, and its not plug and play.

Simon

As I recall he ran two large feeds (4 or 6mm) from the front to the rear, to avoid volts drop. One for the above relay and the second for the supplementary socket. I have towed for many years and find most installers fit too small a feed to the supplementary socket, which then suffers volts drop to the fridge and battery charge circuit and sometimes also causes the voltage sensing relays to oscillate.

If you want to actually wire up the supplementary socket, you will also need the voltage sensing relay. That simply switches the power on to the fridge and battery charge, as the voltage across the main battery rises, as the engine is started and turns it off when you stop the engine.

Either fog lights or reversing lights (not sure which) also work via the supplementary socket.

He also recommends that all connections and joint are properly spliced with solder plus heatshrink for reliability, rather than using those quick blue cable splicers.

[Graham E]

Thanks.
I don't need to really wire the S socket in as I am only towing a trailer but as all the insides of the boot need to come out I may as well wire it all in so if I ever do need it thene it's there.

Thanks guys

[Jakg]

Originally Posted by HarryM1BYT

He also recommends that all connections and joint are properly spliced with solder plus heatshrink for reliability, rather than using those quick blue cable splicers.

"Blue cable splicers" = Scotchloks and are a joke. My car came with a towbar "professionally" wired in with these, and of course after a while all the connections broke.

Replaced with a decent crimp connection and all is good... solder is better but a crimp is just as good and a lot easier.

WRT to power cables - you'll need about 6m of power cable to go from the battery to the boot (or at least 5m gets you to the rear seats). You could probably use 5m if you started at the passenger-side fusebox, though.

I would use some larger wire (like this) just so if you ever need a little more power it's already there - my towbar is wired up with really really small cables and while thats fine for lights, it's not up to any sort of real load.

Originally Posted by HarryM1BYT

If you want to actually wire up the supplementary socket, you will also need the voltage sensing relay

You can also just use a normal relay wired up to something thats live only with the engine (not the ignition). Its something I have to do for my split-charge system.

[Graham E]

So what is best....?

Take power straight from battery or from the fuse box?

If from the battery how hard is it to feed the wires through the bulkhead?

If the fuse box, what fuse do I use?

Would 30amp cable be good enough?

[HarryM1BYT]

You can take it from the battery, the main fuse box, or there is a feed already behind the glove box for the purpose - yellow/red (I think). Where ever you take it from, fit a 25 or 30amp for the supplementary supply and a 10amp for the road lights and as close to where ever you source the supply from as possible. Some suggest a 20amp fuse is adequate for the supplementary supply - with a thin cable and volts drop it might be, but a thicker cable with a fridge and a low battery at the end of it, it would likely blow in time. The 25amp will cope.

The problem isn't so much current capacity as voltage loss or drop along the cables. At 12v you cannot afford to drop much voltage.

[Graham E]

If there is a wire already in place is this connected to the fuse box? If so which fuse?

Is it good enough to take the feed to the lights via one wire and the charging via another?

[Jakg]

Originally Posted by Graham E

So what is best....?

Take power straight from battery or from the fuse box?

If from the battery how hard is it to feed the wires through the bulkhead?

If the fuse box, what fuse do I use?

Would 30amp cable be good enough?

Battery is the best way however for a "low" current draw like yours i'd say that from the fusebox would be fine.

Theres a grommet next to the bonnet release you can use if you decide to go through the bulkhead.

Originally Posted by Graham E

Is it good enough to take the feed to the lights via one wire and the charging via another?

Personally i'd run one cable for both - easier to run one cable, easier to spread the load etc.

[RPWC]

I wired my towing sockets direct to the harness in the boot,ie scotchlocked onto the corresponding wire for the lights ,and the auxiliary socket the same way live to live earth to the body etc including the s/c relay,been like that for two years ,no probs