Help with towball electrics

[Ingwe]

When we bought our van, it was fitted with a tow bar. We suspect, but don't know, that the previous owner may have towed a car.
However, we would like to get a storage box onto a frame that sits on the towball. The box will block the number plate light. So we will need a number plate board which will illuminate the number plate. The box will not obscure the break, rear fog, or reversing lights. Today we went to check the measurements and to check whether the socket worked. I attach a rather poor photo of the towbar socket. I tried to check for voltage using my voltmeter, with the lights off, on, ignition on etc but could get no reading at all. How do I test that the socket works before buying a number plate board?
All, any recommended suppliers of such board. Halfords aren't great.
Thanks

 

[Camping Gaza]

Maypole off of ebay do good cheap lighting boards, different sizes with or without fog lamps free postage.



Silly question, you did earth the black lead to the chassis on your meter when testing didn't you? Sorry in case it slipped your mind.

Socket tester cheap here

 

[tacr2man]

Did you prove you had a good earth at start ?

 

[pappajohn]

If its just the number plate light you could fit a small LED bike type light on a bracket shining on the plate and save a load of trouble.
Your rear lights must be visible from a side angle as well as directly from behind so unless the box is above the rear lights you're going to need a full light board anyway.
If you have to buy a board just plug it in, if it works then fine, if not then worry about the wiring.

 

[pappajohn]

View attachment 307047 Did you prove you had a good earth at start ?

Be aware.... That's looking at the socket from the back.
From the front... Looking at it....
Bottom left.... R/H tail lights
Bottom right... Earth
Center..............L/H side lights

Number plate will be on one of the sidelight pins

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[Ingwe]

Thanks for the replies. Yes, held black lead on the meter to the ironwork (for earth) to which the tow bar is bolted. Then put the red lead in each hole in turn.
Maypole looks a good bet to look. If I can get a reasonable bargain I'll do as pappajohn suggests and just plug and hopefully, play.
The next thing are the boxes. Hugely expensive. Can't really see how a small, aluminium or plastic box can cost over £300! And then there's the bak-rak type mounting nearly £200. They really must see us coming!

 

[Reallyretired]

I have attached a spare wheel carrier to my towbar which obscures the number plate. All I have done is put a number plate to the back box, illuminated by a motorbike type led number plate light plugged into the trailer socket.

 

[Ingwe]

Incdentally Reallyretired, what back box did you opt for? I'm just not prepared to pay the silly Fiamma prices.

 

[autorouter]

As @tacr2man says, first check that the earth pin is connected. To do this, set the meter to Ohms (maybe a symbol Ω that looks like a headphone). The display should show OVERLOAD, OVLD or maybe just OL. Touch the red and black leads together. The display should show a very low ohms figure, typically 0.3ohms. That's the resistance of the test leads.

Push one probe onto the metalwork and the other onto Pin 3(Earth). If it reads low ohms, maybe 0.5 ohms, then the earth is OK. If it stays on OVERLOAD then there's something wrong with the earth connection to Pin 3. None of the trailer lights will work until that's fixed.

 

[Geo]

Incdentally Reallyretired, what back box did you opt for? I'm just not prepared to pay the silly Fiamma prices.

As I read it he didn't fit a box, Just a spare wheel and carrier

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[Ingwe]

@Geo-you may be right but he says "All I have done is put a number plate to the back box..."

Wondered what the back box was, is all.