Help wiring up 3rd brake light

[nlau1 0]

Hey guys.

 

Basically I had a universal 3rd brake light wired up (just plugged into the back of the passenger side rear light). Last month it wasn't working at the MOT test so the MOT guys unplugged it in order for the car to pass.

 

I've now bought a new replacement universal 3rd brake light, but I've forgotten how I originally had the old one wired up. I've managed to get it to work when the headlights are off but as soon as I turn n my sidelights/headlights the 3rd brake light stops working.

 

The way I've wired it is one wire going into the terminal marked "58" and the other wire going into the terminal marked "BR" on the far right as you look at the back of the bulb holder.

 

Can someone confirm whether this is in fact correct (or incorrect as the case may be) and offer anymore insight?

 

Thanks in advance guys

 

Niki

[Stonejag 10]

I did mine into the driver's side rear light but I'm pretty sure the two terminals were next to each other... I'll grab a picture tomorrow if you're still in need :)

 

Only took me twenty seconds to work out with a multimeter, mind - not got one to hand?

 

Stone

[nlau1 0]

Cheers Stone, not got a multimeter to hand unfortunately but would definitely appreciate a pic of your setup!

[davidwort 0]

just follow the metal tracks from the main brake light bulb to rear extra spade terminals on the back of the light unit, that'll give you the +ve and earth you need

[RW1 0]

Brake light positive 12 volts wire at the back plate connector is RH & LH - black with red stripe, earth is brown.

 

The reason it works with no lights is because where you have picked up the "earth", is in fact a +ve to another bulb and the brake lights are managing to earth thro' that bulb circuit to its' earth. Which most likely the rear sidelight 12 volt supply. As soon as sidelights are turned on, the earth wire side of your 3rd brake light goes to 12 volts potential, so "neutralising" the 12 volts of the brake light switch supplied 12 volts. Therefore there is no voltage potential across the 3rd brake light and it won't illuminate.

 

.

[nlau1 0]

RW1 - I don't see any connector marked RH or LH. There's BR and BL though, is that what you mean? and as for the wires of the 3rd brake light they are both black wires so no way of telling which is the earth wire!

[RW1 0]

RH & LH refer to Right Hand & Left Hand as I don't know which side you are tapping into, not that it matters as the wires are the same. It doesn't matter on the 3rd Brake Light which is used as earth or 12 volts. My references are to the Corrado's wiring.

 

31 is earth. BR is your +12 volts for brake light.

 

.

Edited January 18, 2012 by RW1

[nlau1 0]

Ahh I see, I have it wired to BR and 58 which is where I'm going wrong.

 

Thanks for the excellent knowledge as always RW1!

[davidwort 0]

If the 3rd light uses LED's then they may not operate if you get the +ve and -ve the wrong way round, as diodes are directional.

[RW1 0]

Very true, but where did it say LEDs....

 

Or am I just getting senile drawing my pension. :lol:

 

Won't blow the LEDs anyhow.

 

.

[nlau1 0]

They are LED's but I had it wired up wrong anyhow, had it on BR and 58 instead of BR and 31. Thanks to RW1 and davidwort anyway!

[Stonejag 10]

Didn't get back from work in time, sorry! Glad you got it sorted.

 

I learned something new anyway, I didn't realise the four-way connectors on the bulb base accepted spades, I soldered mine onto the tracks :bonk: