Electrical issue

[KEVINJSTANLEY]

Hi Boys
I purchased a tail light addon [RED MINI LED SMOKE Brake Tail Stop Light For Yamaha MT-07] from ebay
it was not what I thought it would be, but nevertheless I attempted to fit onto the rear below existing tail light sitting partially on the number plate.
before I did so I checked it worked [from hong kong] via my drill 12v battery, it did function .
so from there I started to wire it into existing rear light cable just before the 3 pin connector, the unit also has 3 wires and they did function as I said via the battery.
however once wired and reconnected the existing light and gave it ignition, the existing light worked fine but the addon was dead as a dodo.
the addon appears to be led as it the tail light and there was continuity on the cables I split via a split connector.
but nothing from the light. as the light is a sealed unit I could not see if there was power to the addon.

any thoughts would be most welcome

cheers
kev

 

[Ralph]

Could you have the wires the wrong way round led's only work with polarity one way.

 

[KEVINJSTANLEY]

Could you have the wires the wrong way round led's only work with polarity one way.

Hi Ralf
thanks for the reply, I thought I may have done as you suggest, so attempted different scenarios with the three wires, but no joy.
it did not help that the addon came with no wireing diagram although how wrong can you get 3 wires black blue and yellow.

it is annoying, I think I need to stick to domestic electrical work

 

[foxracer]

Does it still work if you test it with your battery again?

 

[Ralph]

When it's on the bike is it earthed to the frame? does it work if you remove that earth?

 

[KEVINJSTANLEY]

When it's on the bike is it earthed to the frame? does it work if you remove that earth?

hi boys

yes it still works via the drill battery, as for the earth it is attached to the tail tidy which in turn is earthed via the frame I assume.
I could make it not be part of the tail tidy to check,
I will let you know thanks to you both for the replies

 

[Ralph]

The other possibility is that it's not earthing via the frame you could try a separate earth wire
to the battery as a test.

 

[Noggie]

I haven't had my entire tail section apart, but I noticed some things are bolted into nuts that is just in contact with plastic and not the frame.
Thinking about it, when I did the indicator and tail tidy job on my bike all lights came with positive and negative wire in the wiring loom, and not just a ground wire to the frame.
This may mean that the battery is not connected to the frame as normal.

Pulling a separate wire could be worth a test.

 

[Ralph]

Many modern bikes do not use the frame for earth's and you often have to run a wire from a known earth.

 

[foxracer]

Yep, took mine apart a few weeks ago and the rear light/brake light has 3 cables one of which is shared neutral. I've not seen anything connected to the frame.

Does the new light work as expected if you remove the existing light completely?

 

[KEVINJSTANLEY]

I have managed to get life out of this cheap bit of bling, we have blue, black yellow, and I put the red from the new unit into the blue and then put black to black we had life, but as soon as brake is applied the new light goes off with existing unit is fine.
so added the yellow to yellow and the new light stays on when brake is applied with existing light staying on but no change to higher intensity as with the existing light [brake light]
earth made no difference so previously it may of just been a bad connector.

so I have a unit that stays on to add to existing but brake light part of it does not function...[waste of time really]