Auto Elec Help Needed - Wiring LED Stop & Tail

Berty

Im going to murder somebody. This is wrecking my head, mainly because I know sweet FA about electrics.

Here is the thing.

I have a stop and tail LED light.

I have tried many times to hook it up. My Audi A4 B7(2006) has a stop and tail, fog and tail(same bulbs) and a regular tail bulb.

From left to right(passenger side) outer stop and tail LED will work perfectly, inner tail light will work perfectly BUT fog and tail section will not accept any LED. I have tried each of them and none of them work in this section but work in the other sections.

Helping items to note:

I do not have a bulb out indicator for low voltage bulbs. I have a resistor. I have connected the + and - with wire connectors sections but to no avail. I have dispensed of the connections and held the end of the resistor wires to each wire(just to see) in both different ways but NOTHING.

Any help please.

bazz26

Berty, drop into Des Kennedy, if anyone knows what is wrong then he will.

Berty

bazz26 wrote: »

Berty, drop into Des Kennedy, if anyone knows what is wrong then he will.

Ah but I want to try to correct it myself rather than having to pay somebody. Being poor and all.

mullingar

Are you installing after market tail light assemblies? or just aftermarket LED bulbs?

Got a pic or linky?

There are 2 important 'features' of LED bulbs.
- the polarity must be correct ie + to + and - to -. If these are wrong, LEDs will not light.
- The very low internal resistance/impendance that the car may not accept but you seem to have covered this.

Get a multimeter and check the voltage polarity for the fog/tail light socket is the same as the brake/tail light.

Berty

mullingar wrote: »

Are you installing after market tail light assemblies? or just aftermarket LED bulbs?

Got a pic or linky?

There are 2 important 'features' of LED bulbs.
- the polarity must be correct ie + to + and - to -. If these are wrong, LEDs will not light.
- The very low internal resistance/impendance that the car may not accept but you seem to have covered this.

Get a multimeter and check the voltage polarity for the fog/tail light socket is the same as the brake/tail light.

Just bulbs and not after market tail lights.

Ok Here is a picture of the bulb set up. The bulb on the left is clearly and LED. It IS definately a stop and tail bulb like any other as it works in the other sections.




I did not include a picture of the resistor but it was working. I know this because it was warm to touch when it was connected. I even connected it both ways between the + & - but alas......................

mullingar

That Bulb is NOT a Stop/Tail bulb. It is a single filament style for either Stop, Fog or tail only.

Standard Stop/Tail bulbs are DUAL FILAMENT bulbs and are marked 5W/21W (tail/stop) with 2 electrical tips, one for tail the other for stop (body is common ground).

Stop or Fog bulbs have 1 tip and are SINGLE FILAMENT. Marked either 5W or 21W

mullingar

This is a Stop/tail bulb.



with 2 electrical tips

mullingar

This is an LED stop/tail bulb with TWO electrical points.

Delta Kilo

But this is an LED bulb, which don't have filaments at all! Maybe when you have your tail lights on only half of them light up or something and when you brake the other half lights up. Are you sure it is the correct resistor? How many ohms is it? My guess it should be around 330

mullingar

Delta Kilo wrote: »

But this is an LED bulb, which don't have filaments at all! Maybe when you have your tail lights on only half of them light up or something and when you brake the other half lights up. Are you sure it is the correct resistor? How many ohms is it? My guess it should be around 330

Its to show that its 2 different lights in 1 bulb, OP may think a single connector LED bulb is a dual stop/tail bulb

Berty

See my picture. Both of those bulbs are stop and tail bulbs.

In the one on the right, the original. Half way up the filament there is an internal bulb which lights up brighter.

These are the same bulbs(LED) I use in the stop and tail which work fine. When they are on they are red and when your press the brake they get brighter.

So Im afraid they are stop and tail bulbs/stop and fog bulbs.

mullingar

IT S NOT A STOP/TAIL BULB. IT IS A STOP (OR FOG) BULB ONLY.

Read the side of the original bulb. If it says 21W with no mention of 5W its a STOP bulb.

Did you not see the electrical differences between your bulbs and the bulbs in my pics????

Bring it into ANY motor factor/garage and they will concur so STOP saying it is.:mad:

Rant over. Your forgiven as you said that you know little of auto-electrics.



Anyway, You give a hint here:

Berty wrote: »

internal bulb which lights up brighter.

Audi may be using a trick here. They may be dropping the voltage to the 21W STOP bulb to make it the same brightness as a 5W tail bulb (eg when your battery is dying in a hand-held torch).

Get a multi-meter and measure the voltage when the tail lights are on. It its 6-8Volts it will confirm this trick. (DONT SHORT OUT THE PINS!!!)

If this is the case the LED bulb is useless unless you fancy modifying the wiring loom.

slimjimmc

Berty wrote: »

See my picture. Both of those bulbs are stop and tail bulbs.

In the one on the right, the original. Half way up the filament there is an internal bulb which lights up brighter.

These are the same bulbs(LED) I use in the stop and tail which work fine. When they are on they are red and when your press the brake they get brighter.

So Im afraid they are stop and tail bulbs/stop and fog bulbs.

Unfortunately I can't see the filaments as your picture is a bit fuzzy and the bulb's hidden behind the wiring, but never mind.

Forgive my confusion, but are you saying that a bulb with 1 electrical contact on the end has 2 filaments just like a traditional 5W/21W bulb?

If this is the case then I can only guess that you have special bulbs where each function (stop/tail) operate at different polarity or voltage. This would require with internal circuitry. I have to say that this would be the first time I've ever heard of such an arrangement.
If you have a multimeter you should be able to check at the bulb holder to see if voltage or polarity changes.


Another possiblity (and most likely imo) is that there's a wiring fault somewhere and that the inner most light is 21W fog only, not 5w/21W tail/fog. It may be pure fluke that when you turn on the tails a small current shorts to the fog light giving the impression of a 5W bulb. Your LED may not be able to operate at this voltage.

A bad earth at the light cluster might cause this.

As I said, only a guess.