3rd Brake Light, to running light?

blazinlow89

Original poster
Member
Jan 25, 2012
2,088
Has anyone tried to get the 3rd brake light to also act as a running light? I have a (crude) diagram that I think would work, but then again I could be wrong.

View attachment 19057

I have the resistor to bring down the voltage to the light so there would be a difference between running/parking, and the diodes would prevent current from back flowing into the other circuit. Not sure one sizes of components.

Any thoughts?
 

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The_Roadie

Lifetime VIP Donor
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Nov 19, 2011
9,957
Portland, OR
That's the right circuit to do it, but I have no confidence that it's legal, being a Federally-regulated safety related item. :confused:
 

Harpo

Member
Dec 4, 2011
411
Sweden
Is that even possible with the neon brakelight we have, isnt it only on or off??.

I doubt that it is dimmable:undecided:
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,053
Brighton, CO
Might not be for the Neon style, but for the Avalanche LED 3rd brake light that some use...

Or people with the XUV, which is also a LED light..

But I always thought the LED's where of the same principal, either on or off..
 

blazinlow89

Original poster
Member
Jan 25, 2012
2,088
That's the reason for the diodes, to prevent backflow from either the running signal or brake signal. The resistor would be in place to bring the voltage down enough to make them dimmer, so there would be a difference between running and brake.

His would be for led lights.
 

ItsOnVoy

Member
Nov 21, 2011
2,401
You will get rear ended for sure doing this lol I do not think its a good idea IMO :no:
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
TollKeeper said:
But I always thought the LED's where of the same principal, either on or off..
This is where a bit of electronics training or experimentation helps out. LEDs are fantastically dimmable, and have the advantage (for me) that they don't change color temperature when dimmed as incandescents do. The filament of an incandescent gets colder and redder as it's dimmed. I have a test system product that uses LEDS (8 different wavelengths/colors) over a 10,000-to-1 dimming range (0.1-1000 Lux), with about 2% accuracy/linearity. It can change intensity and color 15,000 times a second, much faster than the image sensor it's testing can capture a frame.

For automotive use, just vary the resistor value to reduce the current going to the LED. It's approximately linear, so doubling the resistor value from one experiment to the next should cut the perceived brightness in half.

But in this application, many of us don't think it's a good or legal idea to mess with the CHMSL. The lack of aftermarket mod kits to do this may be a hint. And the only person who might take notice to an appearance mod like this would be the person behind you. Who cares what they think?
 

Sparky

Member
Dec 4, 2011
12,927
You would have people thinking that you are either riding your brakes all the time or have an electrical problem.

btw, 02 and 03 had neon 3rd brake lights, 04+ had led.
 

DJones

Member
Jan 21, 2012
701
St. Petersburg, Florida
Sparky said:
You would have people thinking that you are either riding your brakes all the time or have an electrical problem.

:iagree:

btw, 02 and 03 had neon 3rd brake lights, 04+ had led.

I'm never going to change mine. Neon always looks better.
 

Voymom

Member
Feb 3, 2012
2,523
I wouldn't do it either, but it's your truck. I wouldn't want the chances of getting pulled over, getting rear-ended or having people honk at me all the time thinking I was riding my brakes lol. I know I always WTF people who appear to be riding their brakes all the time. I would probably WTF you if I seen you driving in front of me hehe!
 

ItsOnVoy

Member
Nov 21, 2011
2,401
DJones said:
:iagree:



I'm never going to change mine. Neon always looks better.

for LEDs the Avalanche mod is the best! Just wish they had smoked and not just toy with buyers and say it is :no:
 

BO TIE SS

Member
Nov 18, 2011
1,497
I once saw a car with this done. It seriously reduced the effectiveness of the brake light. When they would stop, I didn't notice the change because my eyes had become used to the light being there.
 

RayVoy

Member
Nov 20, 2011
939
BO TIE SS said:
I once saw a car with this done. It seriously reduced the effectiveness of the brake light. When they would stop, I didn't notice the change because my eyes had become used to the light being there.
That's the theory behind the 3rd light; no light then light, "catches the eye".
 

groundshock

Member
Dec 4, 2011
248
About as illegal as killing your wife, stuffing her full of cocaine, and selling her corpse to a van full of kids. Then shooting the kids.
 

fishguy1123

Member
Dec 5, 2011
310
BO TIE SS said:
I once saw a car with this done. It seriously reduced the effectiveness of the brake light. When they would stop, I didn't notice the change because my eyes had become used to the light being there.

Excatly what I was thinking! Not trying to bash the op or anything, just seems like a huge safety risk for him and his passengers as well as anyone behind him. When the 3rd brake light is on it means ur slowing/stoping and thats it! I think we all are only looking out for the safety of all invovled.
 

ItsOnVoy

Member
Nov 21, 2011
2,401
groundshock said:
About as illegal as killing your wife, stuffing her full of cocaine, and selling her corpse to a van full of kids. Then shooting the kids.

Damn :rotfl: As long as they do not do the 3rd brake light mod those kids can get away I believe :rotfl:
 

Sparky

Member
Dec 4, 2011
12,927
groundshock said:
About as illegal as killing your wife, stuffing her full of cocaine, and selling her corpse to a van full of kids. Then shooting the kids.

:crackup: :smiley_kill:
 

blazinlow89

Original poster
Member
Jan 25, 2012
2,088
After considering the quick responses I will NOT be doing this, but I think I can use the same concept else where in the vehicle.
 

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