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3rd brake light bypass

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Old Oct 11, 2016 | 11:09 AM
  #1  
pinhead73's Avatar
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From: Ridgeville, SC
3rd brake light bypass

From what I have been reading, if the 3rd brake light is not on, cruise control does not work and the abs light comes on on the 1994 firebirds and camaros. In my case, I have no 3rd brake light. Is there a way to bypass the 3rd brake light or trick the system into thinking it is there? I have searched but can't seem to find an answer.
Old Oct 11, 2016 | 11:23 AM
  #2  
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Re: 3rd brake light bypass

Why not just keep the the stock socket wired, put a bulb in it, and locate it somewhere in the hatch where it's not visible. Or, measure the resistance of the specified bulb, and put a similar resistor across the two wires for the socket?

Just curious.... why no 3rd brake light (CHMSL)?
Old Oct 11, 2016 | 11:27 AM
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Re: 3rd brake light bypass

Because the car now looks like this.

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I guess I could just run that line. I will have to pick that up on ebay or somewhere.
Old Oct 11, 2016 | 02:47 PM
  #4  
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Re: 3rd brake light bypass

If you removed the wiring already, just find the yellow wire off the brake switch at splice S243, get two resistors that match the resistance of a stock bulb, connect the resistors in parallel (as the bulbs are wired) with each other, attach the yellow wire to one end of the resistor bundle, and a ground wire to the other end of the resistor bundle.

Courtesy of Shoebox

1995 4th Gen F-Body Exterior Lights

http://shbox.com/1/ABS_schematic.jpg
Old Oct 11, 2016 | 04:21 PM
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Re: 3rd brake light bypass

Thank you. That's what I was looking for.
Old Oct 11, 2016 | 10:32 PM
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Re: 3rd brake light bypass

Something to keep in mind is that if you use resistors the same total value as the bulb, they will get very, very hot and could catch fire. Of course the bulb will get hot also, especially if it is covered up. You may want to experiment with some higher resistance value resistors to see what will work. The higher the resistance, the less hot it will get. I suspect anything below about 1000 Ohms will work but don't know for sure. That value will not get very hot.
Another alternative is to use a replacment LED bulb which will run much cooler.

Last edited by GaryDoug; Oct 11, 2016 at 10:35 PM.
Old Oct 11, 2016 | 10:59 PM
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Re: 3rd brake light bypass

How about the relay used to provide resistance load, when swapping the SS spoiler w/ LED'S into a non-SS model. Apparently the relay coil provides an acceptable resistance in the circuit (omit the LED's).

http://shbox.com/1/relay_for_ss_spoiler.jpg
Old Oct 11, 2016 | 11:22 PM
  #8  
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Re: 3rd brake light bypass

That would work and not get too hot. But it may cost more than an LED bulb and harder to select.
One CANBUS 194 or 921 bulb should be enough and ok:
https://www.superbrightleds.com/more...car/1127/2675/

Last edited by GaryDoug; Oct 11, 2016 at 11:29 PM.
Old Oct 12, 2016 | 09:29 AM
  #9  
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Re: 3rd brake light bypass

Originally Posted by Injuneer
How about the relay used to provide resistance load, when swapping the SS spoiler w/ LED'S into a non-SS model. Apparently the relay coil provides an acceptable resistance in the circuit (omit the LED's).

http://shbox.com/1/relay_for_ss_spoiler.jpg

Just to make sure I understand, do the wiring the same with the loop with the relay in between but leave out the led's?
Old Oct 12, 2016 | 07:05 PM
  #10  
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Re: 3rd brake light bypass

Yes. You just need the resistance of the relay coil.
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