Fitted new bulb holders, now lights misbehaving

[THe Maestro]

I had some problems with the rear lights on my GT6 Mk3 working intermittently and I thought that I'd tracked it down to the bulb holders being in pretty poor condition with corroded contact points.  So I bought a new full set of six bulb holders but these each have one more contact than the originals (indicator and reverse lights have 2 contacts each rather than 1, and the brake/sidelights have 3 rather than 2).  I assumed that this was due to the old units earthing themselves through the rear light panels and the new bulb holders each requiring their own earth.  So I removed the earth wire going to the light panel (at each side), split it into 3 wires and connected these to the extra terminal on each bulb holder.  Now the lights are behaving very strangely - the Hazard switch now results in the brake lights flashing rather than the indicators, and the indicators seem to do something different every time I try them.  At first the left indicator was working correctly but not the right one, then they were both coming on but not flashing and now the left indicator is making the right brake light come on even though I've not swapped the wiring around at all.  Can anyone explain this?

[Richard B]

Now that is an earthing fault!

Sure the earth wires you used go to earth?  :-/

Wire up some earth wires that go to the body...

[THe Maestro]

Yes I've tested the black wire going to the lamp panels that I split into three and they are definately earths.  

[THe Maestro]

I've tried making new earths to the body today going to all the lamp holders and it worked intermittently again.  I think I need to inspect the wiring loom running to the back of the car because it may well be damaged at the point where it passes close to the LHS front rear wing because it set on fire while I was welding around there a while ago.  Whats the best way to look at this area of the loom?  If I disconnect everything at the back - lamps and fuel tank sender, can I pull it through from some point near the front of the car to inspect any damage?

[Paudman]

This may be a bum steer but check the connections at your flasher units - my first Spitfire used to flash three indicators on turning right, and a different three on the hazard lights, because someone had connected the flasher units up wrongly.
Otherwise I'll go with the flow and blame the earths.

[THe Maestro]

I don't think its entirely the earths because I've made completely new ones going direct to the body.  I think the wires in the loom are proably all melted inside and crossing over, it was on fire for about 3 minutes.  The first time I checked the original earth (black wires) they seemed ok but then I checked later and they were carrying the flasher signal and later still they didn't work at all.

[Richard B]

That stretch of loom unplugs at the A post.

So either unplug there and pull the lot back into the boot or unplug at the lights and pull it to the front of the car.

Then you can inspect/rectify/overhaul/replace.

(I have burnt a few looms in my time  :'( )

[herald948]

61 wrote:

Yes I've tested the black wire going to the lamp panels that I split into three and they are definately earths.  

Forgive the obvious thought here. I've no doubt your black wires are earth wires, but are you absolutely sure they go to the "earth" terminal on each and every lamp socket?

[THe Maestro]

herald948 wrote:

Forgive the obvious thought here. I've no doubt your black wires are earth wires, but are you absolutely sure they go to the "earth" terminal on each and every lamp socket?

Yep I made sure of that even though I don't think it would make a difference (apart from on the 2 filament brake lights) because these bulb holders don't transmit the earth into the metal clips and into the light panel casing like the old ones did.  

[THe Maestro]

Richard_B wrote:

That stretch of loom unplugs at the A post.

So either unplug there and pull the lot back into the boot or unplug at the lights and pull it to the front of the car.

Then you can inspect/rectify/overhaul/replace.

(I have burnt a few looms in my time  :'( )

Is that the passenger side A-post or does it cross over from the drivers side?  I recall seeing the loom in one of the A-posts but I've never seen any plug/socket arrangement to detach it.

[Paudman]

Yes, passenger side A post up behind the glovebox / fusebox you'll see a large push-in connector linking the two halves of the loom.

[CharlieB]

61 wrote:

So I removed the earth wire going to the light panel (at each side), split it into 3 wires and connected these to the extra terminal on each bulb holder.

Unless I've misunderstood, you've disconnected the earth, connect a wire from one of your terminals to earth ie something on the body, & see if that works.