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Marchin

7 Pin socket and rear fog lights.

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Hello!

 

Altough I am not a caravan owner yet, but I am slowly growing (old enough) to that subject. ;)

 

Self installed towbar 

 

Indicator fault finder works well and loud. (Obviously it works only if  there is a fault - otherwise its silent)

 

One thing that is perplexing me terribly is the fog lamp connection: I had to cut the wire circuit to my left foglight.

 

http://www.hants.pl/photo/hak/wiring_diagram.jpg

 

I was expecting that the small controller will patch the circuit somehow, but now  it is obvious that without my trailer, I have only one right (offside) rear foglight. When trailer is connected, I have all three.

 

Is it legal?

 

It's not a big issue to fix: one relay  few diods and I can mend it, but I was wondering whether it's not the fault, but the feature...

 

 

One more question not really related to electrics, when trailer is attached, do I have to have a break away cable? My ultra-light trailer is used only for the journey to the local tip and does not have independent brakes. 

 

 

 

 

 

 

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You may be confusing stop lights with fog lights!

You refer to having three of them, this would be common for stop lights but probably unique for rear fog lights.

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3 minutes ago, Stevan said:

You may be confusing stop lights with fog lights!

You refer to having three of them, this would be common for stop lights but probably unique for rear fog lights.

 

Oops, apologies, I wasnt very precise. 

 

I do have three stop lights on the car and another two on the trailer lightboard. All works fine here, it is safety critical feature, there should be absolutely no concerns about those circuits.

 

I do have  two rear foglights on my car and one on the trailer lightboard. With trailer detached, only one foglights switches on the car. When trailer is attached (and the dashboard button pressed)- I have all three fog lights on: 2 on the vehicle, and one on the trailer.

 

I wonder whether the MOT tester will be happy with that....

 

 

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With just the connections diagram, but no proper wiring diagram it is hard to see what is happening. It looks like the problem relates to pin 8, the cut off for the fog lights on the car when connected to the trailer. But hard to be certain.

Edited by Stevan

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Been thinking.

 

Looks like pins 2 and 8 must be connected when there is no plug in the socket. By doing so, my two rear foglights would work normally. 

 

Connecting the plug should mechanically disconnect the pin 8 (for whatever reason - perhaps not to create the impression that the stop lights are on - with the three 55W bulbs on).

 

I belive its a mechanical issue in the plug, not the wiring (all joined and soldered to the very high quality).  It just works other way round.

 

Thanks for the tip, Stevan!

 

After the diagnosis I will come back to the forum with explanation.

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8 hours ago, Marchin said:

I wonder whether the MOT tester will be happy with that....

 

The MOT tester doesn't concern himself with N&S7 sockets - only the security of the towbar and ball.

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12 minutes ago, Jaydug said:

 

The MOT tester doesn't concern himself with N&S7 sockets - only the security of the towbar and ball.

And that any fitted fog lights work!

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9 hours ago, Marchin said:

One more question not really related to electrics, when trailer is attached, do I have to have a break away cable? My ultra-light trailer is used only for the journey to the local tip and does not have independent brakes. 

Your ultra light trailer should have a device (chain, cable, metal ring) that both, keeps the trailer attached to the towing vehicle and stops your trailer hitch hitting the road should the hitch become separated from the tow ball.

 

On any trailer* fitted with brakes**,  the brakes must be in working order and a breakaway cable must be fitted and fully operational.

 

*built after 1st October 1982.  Regardless of the weight or size

**compulsory on any trailer of 750 Kg MTPLM or greater

 

edited to add:

Quote

Unbraked trailers must have a stout secondary coupling, such as a chain, which is connected securely to the towing vehicle when it is being towed.  The secondary coupling must be tight enough to prevent the trailer's tow hitch from hitting the ground if the vehicle becomes uncoupled.

 

Braked trailers must be fitted with hydraulically damped coupling and auto reverse brakes to give braking efficiencies required by EEC Directive 71/320.   All wheels must be braked. Braked trailers must be fitted with a breakaway cable. This must be attached to the towing vehicle in such a manner so that, should the trailer become detached, the breakaway cable will operate the trailer's brakes. It is not advisable to connect the breakaway cable to the towball itself, unless it cannot be avoided. Most tow bars have either a drilled hole, or pigtail attachment, specifically intended to accept the breakaway cable's spring clip. 

Braked trailers must be fitted with a parking brake that operates on at least two road wheels on the same axle.


The Law for Trailers

 

 

Edited by ReggiePerrin
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Let me shed some light :D upon this as i can remeber when rear fog lights came in and pin 7 was first used

 

The idea was that turning your fog lights on with a  caravan on the back would cause unnecessary reflection into the vehicle,  as these would be permently on, where the brake lights (Equal intensity) are only on when braking

 

Therefore the vehicle fog lights where looped into the 7 pin socket with a mechanical leaver that broke the circuit to the car fog lights when the caravan was plugged in

 

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Sounds to me as if the spring loaded fog light switch in the car socket is working the wrong way round. It should cut off the car fog lights when the trailer is connected rather than them only working when the trailer is connected. Also for both car fog lights to cut out you need both of them to be wired to the socket and not just one side, unless they have a common feed wire which you have cut. You could check the spring loaded switch without the trailer connected by putting on the car fog lights and then pushing the switch in the socket with something none metallic that will not conduct electricity to avoid blowing any fuses. When not pushing the switch both fog lights should be on, when pushing the switch both fog lights should be off, provided you have wired both fog lights through pins 2 and 8.

 

It might be better to rejoin the car fog light wire you have cut and to take a connection from it to pin 2 on the socket. The wire from pin 8 back to the car fog lights is then not needed. This way the car fog lights will both work whether or not the trailer is connected and the fog light cut off switch is not used (less to go wrong as well).

 

Your wiring diagram shows a 10 amp fuse, all the lighting sockets I have wired up used 15 amp fuses so something for you to check.

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All sorted.  Thank you all for advice!

 

There was a mechanical problem with the switch: metallic connector in the socket was behind the connector - instead of in front of it, hence working "other way round". Overall, a simple fix

 

Also, the wiring diagram did not provide for the eventuality the driver has got two - powered separately - rear fog lights.

At the moment without the trailer - both fog lights can be switched on and off from cockpit. With trailer, only one on the car is switching itself off.

This will be addressed soon, 

 

10A and 14.7V can supply about 150W - it's more than enough for the lightplate, considering that all its power is being taken from the car electrics (without stressing to much any of my 10amp in-car fuses). 

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If you are going to tow a caravan you could find a 10 amp fuse is not high enough since it will have more lights that could be on compared to just a lighting board. They have 6 side lights (each 5 watt), 2 indicators if hazards on (each 21 watt), 2 number plate lights (each 5 watt), 3 brake lights (possibly all  21 watt), 1 fog and 1 reverse (both 21 watt). Without the fog and reverse that is 145 watts that could be on together and at 12 volts is just over 12 amps so a 10 amp fuse could blow as the brakes are applied.

 

If your alternator is giving out 14.7 volts that is a bit high so might be indicating a problem with it. Older ones are about 14.4 volts whereas on newer cars they vary the voltage to save energy so can be less than 13 volts at times.

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