Trailer Adaptor: How Complicated Can it Be?

[jimconline]

I have a 1996 Defender 110 300Tdi that I brought years ago from my work in southern Africa to my home in Canada. I am trying to get the lights to work on the teardrop trailer I just built.

- Have confirmed that the lights on the trailer are all working with a North American standard 4-pin adaptor

- The 7-pin socket on the Defender seems to be wired correctly: I get power at the proper pins for turn indicators, brakes, and running lights

- Purchased two different 7-pin to 4-pin adaptors: both provide turn indicators and running lights; no brake lights

- Opened one adaptor and confirmed that power is coming through for brakes on Pin 6. However, nothing seems to be connected to this pin (red circle in photo). Is there an internal diode that perhaps I am not seeing? If so, why doesn't the power for the brakes flow through the right (green) and left (yellow) turn indicator wires as I believe it should?

My father was a naval aircraft electrician: I'm getting that look from beyond.

[western]

not sure if this will help, https://en.wikipedia.org/wiki/Trailer_connectors_in_North_America

never seen the Nth American 4 pin trailer connections in UK, 

 

the other option is to use a 7 pin connection on the trailer as we do in UK/Europe, then you won;t have any problem with the vehicles wiring.

 

[Blanco]

Many of us aren't familiar at all with a 4 pin system, but it seems to me that the wiring you are showing us isn't what we would expect to see on a 7 pin '12N' socket. Pin 6 which you have circled is where we would expect the brakes to be.

[Blanco]

Following Western's link there it seems clear that your 4 pin system doesn't provide for brake lights, so you will need to upgrade the wiring .

 

[western]

brakelights are a combined operation on the indicator wiring is how I understand it, 

older USA vehicle used the brake lights as indicators for years before the indicator lights changed to amber like UK/Euro vehicles. 

[jimconline]

I have attached a photo of one of the adaptors I purchased; the other is almost identical: one is ProLine and the other says from Land Rover (priced accordingly). Here is a general description:

This handy Flat-4 trailer wiring converter is a plug-n-play solution for Rovers with a stock 7-Way European-style trailer connection. Simply plug it in to your stock 7-way connection and the opposite end has a functional flat-4 standard North American connector to rout to your trailer and enables your brake light and turn signal functions.

I always am hesitant when I read the word simply.

The crux of the problem—and hence the need for an adaptor other than a physical fit—is that the North American 4-pin directs the running lights along a separate wire and runs the brake signal along the two turn indicator wires (as Western pointed out). My understanding is that this adaptor is supposed to do that. Can't see how it does that since the brake in the adaptor isn't connected to anything. Perhaps both these adaptors don't support the brake lights but then, what's their use?

 

[jimconline]

The photo in the original post, Blanco, is from the adaptor, not the 7-pin receptacle on the Defender. I have circled the pin on the adaptor that mates with Pin 6 on the receptacle. So I am getting power when the brakes are pressed but it seems to have no where to go.

[western]

post the adaptor suppliers website info & we can have a look for wiring info. 

[jimconline]

I purchased them both through Rovers North; they can be seen on this url though there is not much info about them: https://www.roversnorth.com/ProductDesc.aspx?code=YMZ500480&type=0&eq=&key=it

I have also written to Rovers North and am hoping to hear back from them soon.

[Roverdrive]

Interesting!

I googled this...

http://www.wiringdiagram21.com/2016/12/trailer-light-wiringdiagram-4-7pin.html

From my understanding the vehicle provides the means of operating both indicators together as brake lights, as well as still allowing one to flash if turning and braking! Might be easier to change the lights on your trailer to have separate brake lights?

Note that the second drawing shows the use as an electrically operated brake rather than a brake light.

 

I also found this

http://www.how-to-build-hotrods.com/turn-signals.html

Half way down is an adapter for the combined indicator / brake lights.

 

Hope this might help you in the right direction

[jimconline]

Thanks Roverdrive. I think your advice about adding brake lights to the trailer is the way to go. On the trailer 7-pin to 4-pin adaptor I tried wiring the brake signal on Pin 6 to the left turn signal on the trailer side (see photo with red wire). The brakes worked the light on the left side of the trailer (proving that brake power is fine). However, with this arrangement, the left turn indicator doesn't work. No idea why.

So, barring any further insights, I shall mount two brake lights, add a wire to the trailer adaptor connected to Pin 6, and run the wire to the back of the trailer, forking off to each new brake light. I think it took me less time to change the timing belt on the Defender.

[Ex Member]

You need a trailer light converter.  Available at any auto parts store.  you would have been better off asking in a North american forum......

https://www.princessauto.com/en/detail/4-way-tail-light-converter/A-p8465841e

http://www.canadiantire.ca/en/pdp/reese-towpower-tail-light-converter-8507900-0409898p.html

[jimconline]

Interestingly, this was my first approach. It failed. I purchased a Curt Taillight Converter (https://www.curtmfg.com/part/56175/) and with great expectations wired it in, tested the feed, plugged in the trailer, and... Only the running lights worked. The rest seemed lost in the flat black converter box. Hence my decision to purchased a 7-pin to 4-pin adaptor which I thought—now in reflection erroneously—would do the trick.

And so, I give up. I have turn indicators and running lights wired directly to a 4-pin plug on the Defender that, when plugged into the 4-pin plug on the trailer, work just fine. So, as others have wisely suggested, I shall add two new pigtails and bulbs to the existing trailer lights and run a separate wire from Pin 6 to the back of the trailer, split in the middle, and run wires from there to the new pigtails. Then I shall have brake lights and all will be complete. Should have done this awhile ago but...

Edited July 17, 2018 by jimconline

[Ex Member]

Then you wired it incorrectly.  The converter must work.  It is all pretty simple.  My best guess is the truck has a bad ground.  It is very common as the light share a common ground that runs back to the single ground point on the bulkhead.  You MUST use a converter to use a North American trailer.  It is the only way it can work.

[jimconline]

I admit that it certainly sounds like user error. But if so, how is it that from the same wires I can get positive readings under load from each input source and power the individual lights on the trailer? All using the same ground. I did have a fleeting thought that the notice on the package of the Curt converter stated that it only works with negative ground vehicle. 1996 Defender 110 are negatively grounded as far as I know. Certainly the negative lead from the battery is wired to the frame.

[Ex Member]

Individually they will work.  If all hooked up at the same time, you are back feeding power to the combined light circuits.  The converter has diodes in it to prevent the back feeding.

You need to find someone to look at it in person that understands electrics.

[jimconline]

√ Running lights   √ Signal lights   √ Brake lights   Solution: start the engine.

I called support for the Curt taillight converter. Didn't mention Defender, simply said that I had wired in the converter to the vehicle, was getting power for all functions from the receptacle into which you plug the trailer, but when I plugged in the trailer only the running lights worked. The technician said that the trailer was drawing too many amps. Then asked, "Is the vehicle running?" When I said no, he said start it up and check it out. He was right. He also mentioned that if this didn't work I may need to purchase a powered taillight converter (#59146) or change the trailer bulbs to LEDs.

Thanks Red90 for getting my head back into the converter.

 

[Roverdrive]

Glad you got to the bottom of it.