Avoiding American tow bar faux par…

[Erie Fred]

Thanks for all the reply’s forumites, they’re all very helpful.

@bricol and @Erie Fred can either of you explain what actually happens on an American trailer with combined brake and indicator light? I can’t quite figure out in my head how that works.

If I can help it I’d like to try and avoid using the brake light, indicator and rear light signals directly from the lights themselves as it was a right pain to get the carapace off with the umbilical cord off tow bar wiring!
Although I could solve that by doing a better job in the first place!

Reverse and fog lights are extras and fitted below the tow hitch. So tapping into those won’t cause s problem.

I don’t know if it had reverse lights originally, I sort of assumed America is so big nobody ever needs to go backwards!

My first post had a link to etrailer, the first link, scroll down, pix of trailer with diagram. including brakes.

As far as reverse, there are no reverse lights on any trailer, as your not allowed to back them up onto
a road. (that is the answer I got from the DOT)...

 

[Martin Hocking]

Red indicator lenses same bulb

Thanks Dave. Does one override the other somehow?

If both brake and indicator wires send voltage to the bulb to light it up, would you not lose the flash everytime you braked. I can’t think of many times you’d be using the indicator without the brakes, especially in an American car.

I think I might be missing something…

 

[Erie Fred]

Yours didn't have the 2nd (rear) fuel tank ????

was very common back then, 2 filler doors, switch in the cab to change front to back.

 

[Martin Hocking]

What did you use on the chassis?

I used jotun 90 epoxy and then overcoated with waxoyl afterwards.
Being me having taken the back off in June last year, i didn’t get round to having it ready to paint until November. So conditions weren’t great at times. I brushed it on and it’s pretty well stuck, so fingers crossed!

 

[Martin Hocking]

Yours didn't have the 2nd (rear) fuel tank ????

was very common back then, 2 filler doors, switch in the cab to change front to back.

Just the one thank god, it costs enough to fill it up as it is!

I’d not heard of the twin tank the internet says the last one was the model before this one in 97.

My first post had a link to etrailer, the first link, scroll down, pix of trailer with diagram. including brakes.

Thanks, I hadn’t seen there were two links.
I still don’t understand how brakes don’t compromise the signal flash.
Why I’m trying to understand is because if the turn signal wires coming into the us socket don’t provide a repeating 12v signal and something clever instead then they won’t be any use to me for a euro tow socket. Which I think is what bricol was getting at in his post earlier on. I’ll have to get the battery back in and the multimeter out as you suggest and investigate what does what.

 

[indy4x]

other useful options with 13 pin are reverse and fog lights for the trailer.
best check mot status as if the socket is visible i understand the mot people test the functions and that all must work

Fogs also work on 7 pin sockets, in the absence of reversing lights the fogs do help illuminate when reversing in the dark

 

[hotponyshoes]

Just the one thank god, it costs enough to fill it up as it is!

I’d not heard of the twin tank the internet says the last one was the model before this one in 97.


Thanks, I hadn’t seen there were two links.
I still don’t understand how brakes don’t compromise the signal flash.
Why I’m trying to understand is because if the turn signal wires coming into the us socket don’t provide a repeating 12v signal and something clever instead then they won’t be any use to me for a euro tow socket. Which I think is what bricol was getting at in his post earlier on. I’ll have to get the battery back in and the multimeter out as you suggest and investigate what does what.

There are at least 2 permitted rear light methods in the USA.
Same as.ours (red & yellow), and the 'old' single red light is still allowed.
On the red method the turn flash DOES compromise the brake light. Ie, if you are turning left and slowing down you'll just have a flashing red.light on the left and a solid red light on the right.
Drive with the hazards.on and you won't have any outer brake lights at all

If your truck has a single filament red bulb that.does both brake and direction the the original American tow bar wiring would be the same and you'll have a problem.

However, if this truck is now in the uk then I'd expect it to be running Red and yellow rear bulbs now?
In which case you can just follow through to the trailer from those.

Also the 'electric brake controller' wire would give a steady signal independent of the indicators but check its actually working when you press the brake pedal. A lot of those are just a wire running from the socket to a point on the dash then you have to fit a separate trailer brake controller up front to send any power down it.

 

[Erie Fred]

Also the 'electric brake controller' wire would give a steady signal independent of the indicators but check its actually working when you press the brake pedal. A lot of those are just a wire running from the socket to a point on the dash then you have to fit a separate trailer brake controller up front to send any power down it.

Yes ^^^ Interesting how your brakes are set-up, we used a separate brake controller at that time, like these:

https://www.etrailer.com/s.aspx?qry=brake+controller

FWIW my 2020 F-150 has an integrated controller, have seen it on most pickups these days.
Works the same way, a variable voltage is sent back to the brakes to actuate.

 

[Erie Fred]

You needn't fear that, the 13 pin is massively more reliable than a 7 pin. My Jeep came with a double 7 pin set 2 years old back in 2016, on the 3rd year the 7 pin quit . It's been 13 pin since then no issues.

7 pin or 7 blade ?
The 7 blade is the most common over here, and the wiping action helps to keep things working better
than the older pin & socket types that seem to get clogged/corroded much more.

 

[Erie Fred]

Just the one thank god, it costs enough to fill it up as it is!

I’d not heard of the twin tank the internet says the last one was the model before this one in 97.


Thanks, I hadn’t seen there were two links.
I still don’t understand how brakes don’t compromise the signal flash.
Why I’m trying to understand is because if the turn signal wires coming into the us socket don’t provide a repeating 12v signal and something clever instead then they won’t be any use to me for a euro tow socket. Which I think is what bricol was getting at in his post earlier on. I’ll have to get the battery back in and the multimeter out as you suggest and investigate what does what.

IIRC 1157 bulb dual filament.

https://www.oreillyauto.com/detail/c/long-life/lighting---electrical/bulb-flasher-fuse/tail-light-bulb/efcb00252345/sylvania-1157-long-life-incandescent-mini-bulb-pack-of-2/syl2/1157llbp

1156 is same in single filament, used for markers, back up, etc.

https://www.oreillyauto.com/detail/c/long-life/lighting---electrical/bulbs/tail-light-bulb/efcb00252345/sylvania-1156-long-life-incandescent-mini-bulb-pack-of-2/syl2/1156llbp

 

[bricol]

Thanks Dave. Does one override the other somehow?

If both brake and indicator wires send voltage to the bulb to light it up, would you not lose the flash everytime you braked. I can’t think of many times you’d be using the indicator without the brakes, especially in an American car.

I think I might be missing something…

As has been said, you simply have a flashing brake light on the side the turn signal is working.
You can get a adaptor in the US to convert "European" turn signals (ie separate amber indicator) to work with US trailers (ie combined brake and turn signal) - it doesn't work backwards, I checked . I did manage to get working turn signals, but hazards flummoxed it.

I bought a trailer connector loom that plugged into my cars rear loom, which while not working as a trailer loom itself, it did give me somewhere to chop into to make UK spec turn signal and brake lights work.

I added a complete new, slim combined brake, tail, and amber turn signal lamp inside my rear lamps, over the original brake light LEDS, using only the brake and amber turn signal part of it as the original tail lights were okay. I simply took additional wires from my relays to run to my trailer socket, via a trailer relay unit (to get the warning required for failed trailer lamps).

To get around the combined brake/turn signal, I took a feed from the front indicators to run the relays for the rear turn signals. And another from the central brake light to run the new rear brake lights.

As your's has been here a while, it should now have amber turn signals and working brake lights - work out where the signals for those have been taken from and use those to trigger your trailer relay unit - you are not going to be able to use the original US trailer connections if it originally had just read rear lights as combined turn and brake lights - which I think it will have, as it's only relatively recently the US started to use amber turn signals more often (it might even have not been allowed by US lighting regs - I know US regs used to control the headlamp size and shape, and kept them as sealed beams (no halogen). Which is why you could walk into a Walmart at 11pm and pick up a replacement head lamp for whatever you were driving, as everything used only a couple of options of round or rectangular units. Which is why you saw Jag XJS, Mercs, Peugeots etc with twin round headlamps instead of the bespoke , styled, lamps they used in Europe).

 

[Erie Fred]

With bed off, it's easier.
Not crawling under it getting dirt all over you, and in your eyes.

 

[Turbo]

I would definitely suggest fitting the 13 pin socket. They are so much better thought out than the 7 pin, better made and a lot less prone to corrosion and bad connections.

You don't have to connect every terminal, just the same ones as a 7 pin.

 

[hotponyshoes]

With bed off, it's easier.
Not crawling under it getting dirt all over you, and in your eyes.

That's a bit extreme just to do some tow bar wiring.
If imagine he would have to crawl under it in the dirt to take the bed off anyway?

Another option.
You can get wireless trailer lights. Just get a set of those then you can just put the transmitter wherever you can find a breakout point for the wires. Might even be able to do that job sat on the drivers seat

 

[Erie Fred]

That's a bit extreme just to do some tow bar wiring.
If imagine he would have to crawl under it in the dirt to take the bed off anyway?

Another option.
You can get wireless trailer lights. Just get a set of those then you can just put the transmitter wherever you can find a breakout point for the wires. Might even be able to do that job sat on the drivers seat

Yes, I was just pointing out, that as he did, in fact remove the bed for frame work.
Making sorting out the lights very much easier standing upright.
As far as wireless, how to run the electric brakes ?

 

[hotponyshoes]

Yes, I was just pointing out, that as he did, in fact remove the bed for frame work.
Making sorting out the lights very much easier standing upright.
As far as wireless, how to run the electric brakes ?

Has he actually got electric brakes on the trailer?
I thought he just ment he could use that feed for trailer brakes lights?

 

[Erie Fred]

Has he actually got electric brakes on the trailer?
I thought he just ment he could use that feed for trailer brakes lights?

I would probably not use the electric brake wire to feed the trailers brake lights.
Previous postings by the OP, led me to think that they wanted to also wire up an
electric brake controller.
What is the allowable trailer weight for an F-150 ?
Is there UK trailers with electric brakes ?

 

[bricol]

Bit of a grey area for US imports never homologated for sale here regarding towing weights - one theory says you can't tow, another the rated towing capacity.

I believe electric trailer brakes are legal under 3500 kg laden - but I've never seen an example here in the UK.

 

[Martin Hocking]

Thanks again for all the input, it’s great!

I think it might be helpful to everyone trying to help me if I make a few clarifications. I didn’t think what I wanted to know was especially specific to the truck itself but I think it seems there’s a bit more variety in trailer wiring than I anticipated.

First for context, the truck is still bedless, much to my dismay!

The point about it being easier to work on with the bed off is quite pertinent, as is the fact that taking it off just to do a bit of trailer wiring is a bit extreme.

If it was as nature intended, taking the bed off wouldn’t be much bother at all, after the bed liner is out of the way it’s six bolts, one electrical connector, a jubilee clip and popping the number plate lights out, then lift off.



So as we are I’d like to sort the trailer socket wiring while it’s easy to get to, and try and keep the bed as easy to get off in the future as possible too.

When it was wired up for trailer life over here with a pair of 7 pin sockets, the bed was effectively sewn on to the chassis with the connections made in the rear lights, with the extra wiring for the fog and reverse lights looping up through the bed from below the bumper, making a right haberdashery of it all.

Hence my desire to use as much as possible of the original us trailer socket harness which lives entirely below deck.

Although as has been pointed out doing isn’t going to be entirely possible, because of the combined brake and indicator and the electric brake feed complicating things. Interestingly it was made with amber indicators but the tow bar socket is for combined indicator and brake lights.

Anyway…

In the time it’s taken me to write this reply I’ve thought about things a bit and I think I can still achieve what I want without making much use of the trailer harness…

 

[Martin Hocking]

This is the harness after the connection I showed in one of the earlier posts.


It splits with one part going to the towbar socket and the other goes to a socket which connects with wires that go to the lights. Five wires which I assume are lights, brake lights, indicators x 2 and either earth or number plate lights. (The original reverse light is on the back of the cab and It didn’t have fog lights)

So presumably I can tap out of those with a nice tidy box as Erie Fred says and a tow relay and keep it all nice and under the bed…

Hopefully doing a nicer job than was done before…

Does anyone have any recommendations for a 13 pin tow relay/ relay kit?