Rear LED Tail light conundrum

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Si Click

Si Click

Well-Known Member
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Location
Lincolnshire
My son's TD5 D90 came with NAS-style LED lights (Britpart?) which have to date worked really well. However, having lifted it by 2" and fitted 255/85/16s, what he did not anticipate was that the larger tyre on the swing away carrier would now contact the tail light when opened - which it did with inevitable results.

He bought a WIPAC branded replacement, but we cannot get it to work in harmony with the other. If we wire the new one in correctly, it functions as you would expect. But the original one on the LHS now works back to front, ie. it is fully bright when the WIPAC is in tail mode and goes to tail mode when you press the brake pedal. It does the same thing if you swap over the red and white wires in the WIPAC. With the WIPAC disconnected the original does not respond to the brake pedal at all.

I am wondering if the WIPAC one has an internal resistor and the originals use an external one, so my first thought was to source a Britpart replacement - but they are all marked WIPAC. His best bet might be to buy another WIPAC and replace them both, but before shelling out for an unsure solution I thought I would tap the knowledge here.

Have any electrical gurus any idea what is happening and how to resolve this?
 
mick the builder said:
Have you played about with the wires. Mine where opposite colours to the loom, very confusing.
Click to expand...

Thanks. We have tried every possible combination of connections. It is not helping that the AMP connectors are reversed left to right - male to left light, female to right light. This does not change the connections, but does mean we cannot just swap from side to side to check they give the same result either way.

What is also a pain is that the wires from the vehicle are not original, only protrude a cm or two from the wheel box, do not follow the spec colour scheme and are probably not connected to the original pin scheme - nor are they the same left to right.

I'll have another go when it stops raining....
 
RHS was the one that got broken. With no RHS light the LHS works fine, but as soon as you connect the WIPAC light it is in brake mode when the RHS is in tail and vie versa.
 
Si Click said:
RHS was the one that got broken. With no RHS light the LHS works fine, but as soon as you connect the WIPAC light it is in brake mode when the RHS is in tail and vie versa.
Click to expand...
Can you test the lights on the cables/loom that appears on the drivers rear corner?
(Behind the cover) you can hen prove the joining loom from right to left is good then.
 
I have not yet gone diving into the loom at the driver's rear quarter beyond accessing the connector for the tail/stop light (3 wires), and testing the light off those wires. The connector is tucked away inside the cabin and disappears through the floor to a space that can be accessed from outside, ideally with the wheel off. As the previous light was working fine, I have no reason to think that the loom itself or the joining loom is defective.

It feels as if we have connected the tail and brake light to the wrong connectors, but I checked the light connections against a spare battery in the garage, and I checked the terminals in the LR with a multimeter. Moreover, we get the same result if we switch the red and white wires over. I'll check it over with a multimeter again tomorrow to confirm that we have got the right connections.
 
Si Click said:
I have not yet gone diving into the loom at the driver's rear quarter beyond accessing the connector for the tail/stop light (3 wires), and testing the light off those wires. The connector is tucked away inside the cabin and disappears through the floor to a space that can be accessed from outside, ideally with the wheel off. As the previous light was working fine, I have no reason to think that the loom itself or the joining loom is defective.

It feels as if we have connected the tail and brake light to the wrong connectors, but I checked the light connections against a spare battery in the garage, and I checked the terminals in the LR with a multimeter. Moreover, we get the same result if we switch the red and white wires over. I'll check it over with a multimeter again tomorrow to confirm that we have got the right connections.
Click to expand...

If the light tests fine, and the loom tests fine, assuming you have tested it correctly, then it should work as it did before.

Even if you connect brake to sidelights, and sidelights to brakes, the lights will operate.

I’m thinking that it’s either an internal fault in the light unit itself, or possibly a short in the loom that has only came to light when you have started moving wires to swap the lights.

I would do two things now, first off test the lamp again on the battery ok the bench, but put a meter on the lead that isn’t connected. So connect earth to battery neg, and brakes to battery pos, and see what happens to the sidelight wire, then swap brake and sides. Secondly, get inside the drivers side rear connection, and remove the link to the passenger side. Connect the lamp (assuming it passes the first test) and see if it works correctly.
 
Sounds good, I'll check tomorrow.
I went over it all again today. Same result, with the new light connected it works as expected, but the old light shows full brilliance when the brake pedal is not depressed, but goes to tail light intensity when the brake is applied. Oddly with the new light not connected the old light does not go to brake light, which suggests there is a dependency across the two lights for brake if not tail light.
 
I had a very similar problem when I fitted LED stop/tail lights and then hooked up a trailer and they all stopped working. It turned out some LED lights have internal circuitry on the stop/tail that means they expect the tail to go off when the stop comes on (and visa versa) and stops the lamp working if the another bulb on the circuit makes the voltage change. Mine only worked in pairs and there was no external reason, it had to be an internal circuit. It sounds like you now have a mismatch, the problem is that the bulbs all look the same and mine did not refer to any internal control / logic circuit on the packet despite there obviously being one. You may end up having to buy a matching pair.
 
rob1miles said:
It sounds like you now have a mismatch, the problem is that the bulbs all look the same and mine did not refer to any internal control / logic circuit on the packet despite there obviously being one. You may end up having to buy a matching pair.
Click to expand...

Thanks that is exactly my conclusion as well. My plan is to buy a Britpart branded one as this should give the best chance of matching the current Britpart installation. However, as Britpart lights are made by WIPAC, it is possible that they have switched to the current WIPAC internals. In which case it will hopefully work with the WIPAC replacement we bought.
 
Before you spend more plug your trailer lights in if you tow, this messed my LED lights up again. They wouldn't work if the trailer had LEDs as well only normal bulbs. I never got to the bottom of it.
 
rob1miles said:
Before you spend more plug your trailer lights in if you tow, this messed my LED lights up again. They wouldn't work if the trailer had LEDs as well only normal bulbs. I never got to the bottom of it.
Click to expand...
Thanks, worth bearing in mind. He doesn't tow (at the moment) and has removed the tow bar. Last time I had a trailer was when I had a catamaran, and I sold that 3 years ago.
 
So with it still not working I finally decided to review my assumptions and test them. The new light (WIPAC made and branded) has black, white and red wires which I had proven were earth, tail and brake light. The old light (WIPAC made, BRITPART branded) had the same colour wires and I had assumed that black was the earth.

Ten seconds with a standalone 12V battery showed that on the old light the white wire was the earth. WTF?
With that knowledge it was possible to wire it so it worked. But why would anyone have white as earth?
 
OK your problem was different to mine. And yes, as I found out the hard way on my LED rear fog, white must be earth in China! They also seem quite happy to use red or black for live.
 
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