Rear light problems

[Oli.g]

Hi ive had a problem with my tail lights on my collie for a while, its coming up to mot time so decided to buy new ones..

I used to have very dim tail lights and with lights on only one side lit up but all brake lights worked. Lights turned off my top and the opposite side lit up as a brake light.

Just fitted my new ones after digging out a gardem full of mud from my rear bumper and noticed there is barely any of the metal bumper bracket/reinforcement left (rust)

Do the tail lights need to be bolted to that metal braket to earth or do they have an earth wire on the harness or something? As you cam tell im no mechanic

Thank you for any help

 

[AdventureWagon]

Hi mate classic earthing issue this sounds like. Yes they certainly need an earth from somewhere if not from the loom then they must have a metallic connection to the body. Remember a multimeter is of little use here, the connection from bulb to earth will seem fine on a meter but the second you try and put 2A or so from a taillight on it you'll get the symptoms you see.

 

[AdventureWagon]

And

Hi mate classic earthing issue this sounds like. Yes they certainly need an earth from somewhere if not from the loom then they must have a metallic connection to the body. Remember a multimeter is of little use here, the connection from bulb to earth will seem fine on a meter but the second you try and put 2A or so from a taillight on it you'll get the symptoms you see.

And by body I just mean anywhere on the body does not have to be your rusty bracket but if you want to clean that up there's no problem using that. Sometimes though it's just easier to run a wire from the body to the lights

 

[Shayne]

I think the bit you mean is just reinforcement and unnecessary . Remember your tow socket is pretty much a third light so a short caused by rot in there will affect things .

 

[Oli.g]

Thank you for your reply!

The actual lights are litrally just bolted to the plastic bumper now and plugged in, not on any kind of metal. I wasnt sure if the mounting bolts of the tail lights were what earth onto the bumper reinforcement/crash bar.

Im probably making no sense at all here, im sorry if so haha

I dont have a tow bar fitted, i have a little loom to my left rear light with a plug to the tail light and same on the right, cant see any other wiring.

Hopefully the previous owner hasnt butured it all!

 

[Shayne]

So the new bumper lights are working ok yes ?

 

[Oli.g]

Yes shayne, there all working, indicators and brake lights all have power and light up. Just not correctly haha.

I turn my lights on and on the passenger side: brake light lights up as running light/tail light.

Drivers side:idicator and brake light light up as running light/tail light.

Indicate left and passenger side indicator flashes and brake light lights up and flashes each flash of the indicator

Indicate right and drivers side brake light lights up brighter as an indicator.

They have a mind of there own
Im wondering if its an earth or the wiring, the new lights could be wired different on the plug but before i go cutting and playing with bullet conectors i thought id ask the experts

Thanks for all the replies i appreciate the help

 

[Oli.g]

With the lights turned off:
When i push the brakes, passenger side indicator and brake light both light up.
Drivers side brake light lights up.

Indicate left and the passenger indicator and brake light both flash together.

Indicate right and just the driver brake light flashes.

 

[Shayne]

That kind of behavior is almost certainly a bad earth - but where ?

There's one in with your jack i think and it might be worth taking a look around your headlights because obvious front and rear are connected .

 

[AdventureWagon]

You could temporarily add another earth to the light bulb earth and see if that sorts it out.

My trailer had similar symptoms and drove me mad as we were about to leave for a trip. Ended up running another earth from the tow plug to the trailer chassis as a 'temporary' solution

 

[Bob]

The bumper lights are best replaced at that stage.. I drilled the units out and put new bulb holders in, but full units would be even better. It would solve the issue for little outlay. Chasing electrical Gremlins can be infuriating

 

[Finiterex]

The white/black cable in the rear light loom is the common earth. If you've aftermarket tow bar electrics I'll guarantee you the problem will be either where its been spliced into the loom (joints rotten with the rot likely extending into the original loom) or it will be the tow hookup itself shorting.

My advise is always the same. Strip out the toe bar electrics, inspect where it was spliced and repair. You may well need to replace bits of the loom if the splices have rotten badly.

Oh and if the new units aren't genuine it's highly likely they are wired up differently. If you want a copy of the wiring diagram let me know.

 

[EvoLC]

The white/black cable in the rear light loom is the common earth. If you've aftermarket tow bar electrics I'll guarantee you the problem will be either where its been spliced into the loom (joints rotten with the rot likely extending into the original loom) or it will be the tow hookup itself shorting.

My advise is always the same. Strip out the toe bar electrics, inspect where it was spliced and repair. You may well need to replace bits of the loom if the splices have rotten badly.

Oh and if the new units aren't genuine it's highly likely they are wired up differently. If you want a copy of the wiring diagram let me know.

Hi, I have a 98 Colorado with a tow bar and my rear lights have packed in. I think I need this diagram, also where to get the loom and connectors from for a 98 Colorado? Many thanks. Adam.

 

[MikeJak]

just seen your post, and remembered... I had a similar issue when I first bought my 90... original lights were rusted and the new ones I bought were wired wrong. they have an earth line in the loom but the pins were assembled wrong.
I bought the rear lights from ebay, just chinese copies and they have been fine for a few yars, less then 20pounds per side... it just looks like they chuck the pins in the connectors a bit casually in the factory. you can pick the pins out of the connectors and place them i the correct order.