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Aftermarket brake lights for rat rod.
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Coffee Freak
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Location: Lexington, NC
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PostPosted: Tue Mar 28, 2017 5:43 am    Post subject: Aftermarket brake lights for rat rod. Reply with quote

I'm looking to mount some aftermarket trailer style lights on my rat rod in place of the tombstone style ones (going fenderless). I pulled out the trusty wiring diagram here:

https://www.thesamba.com/vw/archives/info/wiring/bug_std_super_72.jpg

And have narrowed the brake and turn wires down into white, red and black wires. The turn signals I want to use have just two wires and ground through the chassis. It appears that the white wire comes from the light switch and the red come from the brake light switches on the master cylinder. Am I overthinking this, or to I just connect the two wires together and connect them to the brake light wire on the new brake light? I can tell that the black wire is the turn signal light and will go to the turn signal wire on the new light. Brown and blue will go to a new reverse light independent of the new tail lights.


I don't currently have a battery in the vehicle so I cant test with a test light otherwise I would have..... Smile
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windfish
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PostPosted: Tue Mar 28, 2017 6:52 am    Post subject: Re: Aftermarket brake lights for rat rod. Reply with quote

Yep, your bug uses different bulbs for brake and turn signals and most trailer lights use the same bulb.

Can pick up an adapter made just for this
Image may have been reduced in size. Click image to view fullscreen.

Most autoparts / rv / trailer stores carry them.

Consider soldering the wires instead of those awful guillotine splice things.
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runamoc Premium Member
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PostPosted: Tue Mar 28, 2017 9:29 am    Post subject: Re: Aftermarket brake lights for rat rod. Reply with quote

Quote:
I don't currently have a battery in the vehicle


Do you have a battery charger? If you do, use it in place of the battery. Think of it as a 12volt power supply. Wink
_________________
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VW Wiring = It's just wires
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ashman40
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PostPosted: Tue Mar 28, 2017 11:08 am    Post subject: Re: Aftermarket brake lights for rat rod. Reply with quote

Coffee Freak wrote:
And have narrowed the brake and turn wires down into white, red and black wires.

The wire colors you are quoting are the wires in the taillights. Here are the wire colors in the wiring harness that runs to the rear of the car:
    grey/black = left parking lights
    grey/red = right parking lights
    black/red = brake lights (one wire comes from the MC which splits at the rear of the car into two wires)
    black/white = left turn signal
    black/green = right turn signal
    black = reverse lights

From the factory there were four separate circuits (four wires) on each side of the car plus a fifth brown ground wire which was grounded at a screw inside the engine compartment The bulbs shared this ground wire.


Coffee Freak wrote:
The turn signals I want to use have just two wires and ground through the chassis. It appears that the white wire comes from the light switch and the red come from the brake light switches on the master cylinder. Am I overthinking this, or to I just connect the two wires together and connect them to the brake light wire on the new brake light?

It is likely your new taillights have only two bulb filaments (either two bulbs or one bulb w/ two filaments), one low watt (5W) filament for parking lights and one high watt (21W) filament for brakes or turn signals. Even if they are LEDs the wattage will be lower but one dim and one bright. The 21W bulbs will be noticeably brighter than the 5W bulbs. It is the bulb that determines how bright the light will be not the wires. All wires into the taillight deliver 12v and could power either a 5W or 21W bulb.

The stock taillights each had two separate 21W bulbs, one for turn signals and one for brakes. There was a reason for this. When you are at a stop light (brake lights ON) and signaling for a turn (turn signal flashing) you need to represent BOTH conditions. If you just combined the two circuits into a single 21W bulb the brake lights would always keep the bulb powered even if the turn signal output was pulsing. So at the stop light your turn signals lights would not flash.

Combining the parking light wire and the brake wire into a single bulb filament would mean the brake lights would do nothing at night when the parking lights were ON. The parking lights would provide 12v to the bulb all the time. Stepping on the brakes would not make them any brighter, they are already fully ON because the parking light circuit is powering them... really bad since night time is when you need brake lights the most!o

No, you cannot just merge two wires together and expect a useful result. You need a "black box" like the one windfish posted. This box combines the turn signal and brake circuits into a single bulb in a functional/smart way. If the turn signal and brakes are both ON, it will continue to pulse the light on that side.


Coffee Freak wrote:
I can tell that the black wire is the turn signal light and will go to the turn signal wire on the new light.

Another option which works is to buy two sets of NEW taillights. The 5W bulb in all four will be the parking lights. The 21W bulbs in one pair will be the brakes while the 21W bulbs in the other will be the turn signals. You get a cool look and full function without the need for a "black box"


Coffee Freak wrote:
Brown and blue will go to a new reverse light independent of the new tail lights.

Brown is ground. Both your taillights and reverse lights will BOTH need a ground wire. Grounding thru the body is not very effective. The fender bolts will rust over time and you get bad grounds. If necessary, tap a hole inside the new light assembly and run an extra ground wire. Ground it to the ground screw inside the engine compartment where is will be somewhat protected from the elements.
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'67 Beetle #1 {project car that never made it to the road Sad }
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Coffee Freak
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PostPosted: Tue Mar 28, 2017 4:52 pm    Post subject: Re: Aftermarket brake lights for rat rod. Reply with quote

ashman40 wrote:
Coffee Freak wrote:
And have narrowed the brake and turn wires down into white, red and black wires.

The wire colors you are quoting are the wires in the taillights. Here are the wire colors in the wiring harness that runs to the rear of the car:
    grey/black = left parking lights
    grey/red = right parking lights
    black/red = brake lights (one wire comes from the MC which splits at the rear of the car into two wires)
    black/white = left turn signal
    black/green = right turn signal
    black = reverse lights

From the factory there were four separate circuits (four wires) on each side of the car plus a fifth brown ground wire which was grounded at a screw inside the engine compartment The bulbs shared this ground wire.


Coffee Freak wrote:
The turn signals I want to use have just two wires and ground through the chassis. It appears that the white wire comes from the light switch and the red come from the brake light switches on the master cylinder. Am I overthinking this, or to I just connect the two wires together and connect them to the brake light wire on the new brake light?

It is likely your new taillights have only two bulb filaments (either two bulbs or one bulb w/ two filaments), one low watt (5W) filament for parking lights and one high watt (21W) filament for brakes or turn signals. Even if they are LEDs the wattage will be lower but one dim and one bright. The 21W bulbs will be noticeably brighter than the 5W bulbs. It is the bulb that determines how bright the light will be not the wires. All wires into the taillight deliver 12v and could power either a 5W or 21W bulb.

The stock taillights each had two separate 21W bulbs, one for turn signals and one for brakes. There was a reason for this. When you are at a stop light (brake lights ON) and signaling for a turn (turn signal flashing) you need to represent BOTH conditions. If you just combined the two circuits into a single 21W bulb the brake lights would always keep the bulb powered even if the turn signal output was pulsing. So at the stop light your turn signals lights would not flash.

Combining the parking light wire and the brake wire into a single bulb filament would mean the brake lights would do nothing at night when the parking lights were ON. The parking lights would provide 12v to the bulb all the time. Stepping on the brakes would not make them any brighter, they are already fully ON because the parking light circuit is powering them... really bad since night time is when you need brake lights the most!o

No, you cannot just merge two wires together and expect a useful result. You need a "black box" like the one windfish posted. This box combines the turn signal and brake circuits into a single bulb in a functional/smart way. If the turn signal and brakes are both ON, it will continue to pulse the light on that side.


Coffee Freak wrote:
I can tell that the black wire is the turn signal light and will go to the turn signal wire on the new light.

Another option which works is to buy two sets of NEW taillights. The 5W bulb in all four will be the parking lights. The 21W bulbs in one pair will be the brakes while the 21W bulbs in the other will be the turn signals. You get a cool look and full function without the need for a "black box"


Coffee Freak wrote:
Brown and blue will go to a new reverse light independent of the new tail lights.

Brown is ground. Both your taillights and reverse lights will BOTH need a ground wire. Grounding thru the body is not very effective. The fender bolts will rust over time and you get bad grounds. If necessary, tap a hole inside the new light assembly and run an extra ground wire. Ground it to the ground screw inside the engine compartment where is will be somewhat protected from the elements.


I think I'm going to do as you suggest and get an additional pair of lights to use as running lights. The reviews I've seen for the "black boxes" have been about 50/50 and I found some cheapie motorcycle turn signals I can use for the running lights.
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