Side light problem

[Telf 224 2 Cars]

So my rear lights are working on sidelight selection but the fronts aren't. There's no power it seems . I thought they are all powered off the same source so I'm confused. Anybody have any idea?

[Andy 105 1 Cars]

I recently rewired the front end of my car back to the fuse box. O/s and n/s have separate feeds back to the box,  but I assume have the same power supply front and rear . Are you sure that the front does not show 12v with lights on? If so, did you replace the 2 pin connector to each side light ? The terminals can get very corroded and give no connection to the lamp . 

 

[jackherer 543]

I saw you had new connectors on the near side already but the wire itself is probably corroded a fair way back so you'll need to cut it back until it is good and splice in new wire on both sides.

[Telf 224 2 Cars]

So...

I have rear side lights . Both are working fine. However when I put the switch the sidelights on a fuse pops . It's the second on the right from the edge. So I have rear lights but no front side lights. It seems they are on different power supplies front and rear. Anyway I tested the power lines to the fronts . One side is earthed on both cables. The other only on the correct earth cable. 

 

So clearly a short to earth.my question is does anybody know which plug in the fuse box feeds the driver's side light? I think I'm going to have to replace the cable as it's clearly shorted somewhere

[Telf 224 2 Cars]

I've also disconnected the plug at the fusebox that goes to the light switch on the steering wheel column so I know the short isn't in that part of the circuit. Indeed it can't be or both front and rear sidelight fuses would be popping

[Telf 224 2 Cars]

I'm thinking this might helpe in some way ID which fuse is feeding which loom...

[Andy 105 1 Cars]

Yes. Plugs B and C . B is white and C is brown . On the white plug, pin 3 ( green wire 56) and on the brown one , pin 2 ( green55)  . Brown is offside, White is nearside. Hope this helps narrow things down a bit 

Andy

[Telf 224 2 Cars]

So here's my logic... Bare with me. Looking at the diagram both front side lights share the same fuse. Both are linked via K5 and V1 to the instrument console and via M1 to the fog lamp switch. The steering column switch is via R7. See photos.

[Telf 224 2 Cars]

I only have short to earth on the driver's side not the passenger . This is confusing as they are according to the diagram linked to fuse F13. So if one power line is short to earth you should be able to detect it on both but it isn't true. 

 

The cabling from the switch via R7 isn't at fault as when you pull that plug out the fuse box the earth condition remains.

 

I haven't disconnected plug V yet or K which would remove the cabling from the instrument console and fog light.

 

I just can't get my head around the fact that if the diagram is right a earth short on one of the sidelights should be showing up on the other as they are linked according to the diagram.

[Telf 224 2 Cars]

Having sat and thought about it I'm also certain I've seen the sidelight indicator come on during the build which would indicate it did work at some point...

[Andy 105 1 Cars]

Depends where you put your probe from your multimeter . If you disconnect both plugs B and C , you can easily check if the power feed to each front lamp is grounded or not without getting any bypass effect on the internal wiring of the fuse box . That will tell you if the positive supply from the fuse box to the relevant front light is faulty ( ie grounded ) . Then, as you say, replace the offending wire from the appropriate plug to the corresponding light .

 

[jackherer 543]

1 hour ago, Telf said:

I just can't get my head around the fact that if the diagram is right a earth short on one of the sidelights should be showing up on the other as they are linked according to the diagram.

Like I said before the wire is probably corroded on one side at least which would mean you're not getting continuity to your short on the other side.

[Telf 224 2 Cars]

I've taken 1/2 the console to bits .. I found that when I disconnected plug K the earth signal stopped . Thinking this was something to do with the instrument panel from K5 I took all those plugs off too. No luck. So I disconnected the earth under the dash and with K connected the earth signal went again... So I've checked the earth cables off the multi earth there under the dash. . I found 1 of the cables kept the earth signal on but the rest didn't . 

 

Traced again . Now I find that I've plugged this twin cable pictured into the earth block that's just above the fuse box. With it disconnected and everything else connected no more earth on the live sidelight cable.

 

This twin cable is labelled M10A and M10B . I can't find them on the diagrams. Any idea please?

[jackherer 543]

Glovebox light switch. It must share the same fuse I guess?

 

[Andy 105 1 Cars]

Looks like it is F7 for the glovebox. However, F7 and F13 ( sidelights) end up at a common point at the dashboard dimmer switch. Come to think of it, I had problems with that popping fuses when it was  moved to one extreme of its  travel( full brightness) . A fault on that dimmer switch willhave the effect of grounding the live , which could well give all the problems you  have . 

Andy

[jackherer 543]

Your dimmer must have been shorting to ground when you moved it, I've bridged the dimmer entirely with wire before and that works fine.

 

The only time I had a problem with the dimmer blowing fuses was in a stripped out track car where I bolted it directly to the steering column without realising the exposed metal on the dimmer is live!

[Telf 224 2 Cars]

Cheers guys . Shortly after posting I worked it out by following the cable back and it dawned on me what was happening. So frustrating!!! So it's rebuilt now and nearly MOT ready