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MG Midget and Sprite Technical - number plate light electrics

Hi Guys, hope you can help again, you usually come up trumps, so here goes, on my 74 RWA I have taken off the rear bumpers as you all know they house the number plate lights, To counter-act this I have copied Rob's midget idea and fitted an original Mk1 light above the number plate to take the place of the ones built into the bumpers.

Now for the problem, I have disconnected the bumper light wires, one red and one black on each side, with my limited car elec knowledge ie: none,

I thought all I needed to do was to connect the live (red) and earth (black) to either one of the old connections, but I can connected the black, but when I connect the red to side lights red, I blow a fuse and end up with one side light front and back! any ideas as to what I'm doing wrong, and what I need to do.

cheers Lads

Jack.
Jack New Forest

Are you saying that your new light has both a red and a black wire?

If so, and connecting the red to red blows the fuse, either there is a short between the red and black in the lamp, or the connections within the lamp are reversed and the lamp is earthing through the body and shorting the red to earth.

Any chance of a photo of the lamp internals?
Dave O'Neill 2

Hi Dave, thats good info, should I undo the lamp and reverse the connections I'll have a look at that! and I'll take a pic.
cheers jack.
Jack New Forest

I wouldn't recommend reversing the connections until we are sure what we are dealing with.
A pic would be good to start with.
Dave O'Neill 2

Good job the side-light circuit is fused... or else you'd be melting the insulation around the wire all the way down the loom... maybe even start a fire...

Why not check the connections on the MK1 light assembly, so you are 100% certain it's: a) working fine, i.e. no internal short, and b) which way round to connect it.

Check the bulb's OK too.

A
Anthony Cutler

Thanks Guys, Anthony your scaring me! I'll post a pic today, Anthony you look like you have got the same problem on your profile pic, one front light lol.

cheers Jack.
Jack New Forest

Hi Dave, I have taken a pic of the light perhaps you could have a look see if you see anything unusual, don't worry about the blue cable, I ran out of red! but i think they are in the correct position.

cheers.


Jack New Forest

Jack

Your wires are the wrong way round . Your blue (red substitute) is earthed and your black is connected to the live terminal.

Trev
T Mason

As above!

The centre terminal - which currently has the black wire connected - is insulated from the lamp body by the brown piece which it is rivetted to. That's where your live (red) should be.
Dave O'Neill 2

plus you appear to have bare wires protruding from the (bullet?) connector

the wire insulation should not end before the connector, a good habit to keep all wires fully insulated

(my monitor is too dark to see the photo properly)
Nigel Atkins

mine too Nigel

Couldn't even see the black centre wire

glasses

I need my glasses, anybody see where I left them?
Bill 1

Great info guys I knew you would get me out of trouble, and also show up my lack of electrical know how! still we can't be good at everything, good golfer! good drummer in my rock n' roll band! but when it comes to wires and that power you can't see Electricity! I'm beat! well done boys I'll let you know how I get on tomorrow, listen out for the bang! lol

cheers Jack.
Jack New Forest

Well boys still no luck, I changed the wires over, so the middle connection is live and the end connection earth, I have made them neater with no bare wires showing Nigel, and still blowing the fuse, I have connected everything back the way it was and all works well, so starting from scratch again, for testing purposes:

1) If I pull out the red and black from say the nearside bumper light and put my live and earth where they would have gone, would that light up my new number plate light? or do I have to disconnect both sides?

2) Should I try and connect the earth directly to the car?

3) I'm running out of fuses so don't want to mess up anymore.

4) When I disconnect both the bumper lights, and connect my two new wires to earth and live, am I not completeing the circuit somewhere?

Question, the sidelights where are they earthed to because they don't have a black going into them, are they earth through the body of the light to car?

it's getting crazy now, I thought this would be simple, or is it me that is simple, don't answer that one! good job I'm not rewiring my house, I would probably knock out the whole of Southampton grid!

help!!!!!!!!
Jack New Forest

1) Yes, that SHOULD work.

2) shouldn't make any difference.

4) Yes

5) Yes, sidelights and tail-lights earth through the lamp body.


If you are still blowing fuses with it connected correctly, that would suggest that the light is faulty - i.e. there is a short between the live side and the lamp body/ground.
Dave O'Neill 2

OK Dave got all that, I'll try and disconnect nearside bumper lights and put new connections in place, if I blow the fuse, I'll take the new light off and inspect it, it is new proper lucas as well not a copy, should be good!

cheers Jack.
Jack New Forest

Dave, Just disconnected the offside bumper lights, took the new lamps off, pulled out connections rechecked lamp connections, put back in, eh! presto the new lamp is working, have disconnected the nearside bumper and the new lamp is still working yipee! I would buy you a pint but it's a long way to Solihull.

cheers Jack.

ps: I have taken the new lamp off the body it is just loose, could the problem be with the lamp when bolted to body, or was it just bad connections shorting out?
Jack New Forest

I was going to suggest removing from the body, but that shouldn't make any difference, as the the black wire goes to the lamp body.

You may have 'disturbed' the short when removing it from the car.

I would look very carefully at the centre contact where it is rivetted to the brown board in case it could be shorting against the lamp body somehow.
Dave O'Neill 2

This thread was discussed between 14/03/2011 and 16/03/2011

MG Midget and Sprite Technical index

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