# Wiring help?



## Jman (Jan 31, 2011)

I am not a mechanic but trying to learn. Have 6 tail lights working but when I press brake pedal nothing changes. I have been able to eliminate the switch at the pedal but don't know what else it might be. Any input would be appreciated.Thanks


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## Rukee (Feb 8, 2007)

Welcome to the forums.
How did you eliminate the brake switch?? Did it have power on both sides when the brake is pushed?? If so, then did you test the rear light sockets with a test light mounted to a known good ground with the brake on?


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## Jman (Jan 31, 2011)

To eliminate the switch I checked for continuity with volt meter and it has it when brake pedal is depressed and doesn't when not. I didn't check the sockets because all 6 tail lights work and they seemed to be grounded by the housing so don't know how to check them when pulled. However I did clean all contacts on the sockets and bulbs and I ran continuity on both sides of the bulbs and they are good so that's where I get lost.


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## dimitri (Feb 13, 2009)

Continuity on light bulbs is not a good way to check. The filiment can be cracked still showing contiuity and not work. I would put a new one in and see if it works. 

When you remove the bulb inside the socket you will see two contact points at the bottom. With a test light probe them. One is for lights and one is for brakes. I have both a test light and volt meter. For touble shooting it is better to use a test light. You can buy them at Kragen cheap. For a good ground I take some jumper cables from the negative terminal of the battery to where I am working. You might have to sting a few together, but it is a great ground.


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## Jman (Jan 31, 2011)

Ok, I will try that. Thanks


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## comerz1 (Jan 15, 2011)

My first question would be are the turn signals working?

Do you have 12v at the brake light switch?

If neither of these are present then I would check fuses and flasher.

One other thought, take a length of wire long enough to go from brake light wire at light to under the dash, attach to brake light wire, and check ohm from that wire to wire on back of brake switch, just to be sure it hasn't broken or been comprimised in any way.

However, I am thinking it may be the flasher, they are NC (normally closed), and for some reason it may have stuck open which would leave you with no brake lights unless the blinkers are on a seperate light from the brake lights, then we are back to square one.


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## Jman (Jan 31, 2011)

ok, have power at brake foot switch. when i use switch or a jumper to complete the circuit it does nothing for the brakes even though all six tail lights work and brake foot switch only has power with ignition on. also blinker works on driver side front and rear, neither work on passenger side. tail/brake light sockets have 2 wires going to them and i am guessing one for tail and one for brake, they seem to ground in fixture but some work out of fixture and some do not so now what? 

i am just more confused


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## Jman (Jan 31, 2011)

btw to answer earlier question, when i pull socket that works out of fixture with headlights on i can get power to one side (guessing the light side) but not the other with ignition on, lights on and brake pressed

also, my fuse box labels are no longer there and i cant find a diagram to know which fuse controls brakes


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## dimitri (Feb 13, 2009)

With the brake switch jumped, lights and turn signal off, remove the light bulbs and with your test light connected to ground probe the the contacts at the bottom of the socket one at a time. Be carefull not to touch the side of the socket when you are doing this, it will short out. If your test light comes on one of the contacs that is your brake circuit. You have a problem with your light sockets. If the test light does not come on, you have a break in the wire between the socket and brake switch which is probably some where in the trunk or where it comes through the trunck or bumper area. It can be right were the wire ends at the socket and is crimped onto the contact. I really think you have a problem with the sockets.


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## Jman (Jan 31, 2011)

thanks for the detailed instructions, it makes sense to me now. i hooked up a long ground wire direct from the battery but the only thing that makes me think it is something other than the sockets is that none of the brakes work and all of the tail lights work and it seems odd that all six sockets would be bad at once but i will try what you said and get back. thanks again, i am really trying to learn to be a better mechanic but as of right now i need all the help i can get!


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## dimitri (Feb 13, 2009)

Keep us informed. Well get it.......


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## Jman (Jan 31, 2011)

ok cant get anything on left side yet but got right side to work and they go in and out and get brighter by wiggling wires so i am trying to find six new sockets and i will just rewire the whole thing but what i am trying to find a wiring diagram because 4 wires come from the front of the vehicle to run 6 tail lights 6 brake lights and 2 reverse lights and blinkers too so how does that all work?


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## dimitri (Feb 13, 2009)

Start unwrapping the tape from the wire socket and you will see the wires you need to cut and splice. With the lights on, brakes off use your test light to probe the contacts at the bottom of the socket to determine which is the light circuit. You should be able to see what color wire it is. This will be the same color for all rear sockets. If you look closely at a double filiment light bulb, you will see a thin filiment and a thick one. The thick one is your brake filiment. On your light circuit power goes in on one of those contacts on the bottom and straight to ground (the case of the bulb). The brake circuit goes in on the other contact and the to ground.


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## Jman (Jan 31, 2011)

whoa, i never noticed a difference in the filaments, i thought either way would be ok so thanks for that, i am going to get a soldering iron and heat gun and shrink tubes tomorrow so i can do this up right (i hope) but how do the turn signals and reverse lights come in to play? i know one wire prob runs all six brake lights and one wire runs all six tail lights and one wire could run both reverse lights but that only leaves one wire for 2 blinkers which have to be separate otherwise they would both flash, right? i would like to start at the four wires and completely re-wire all of it cause it looks like it has been done kinda shady and i think re-wiring all of it would be better? i may be getting in over my head i just realized that the license plate light is in effect also, dang there is a lot going on back there


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## dimitri (Feb 13, 2009)

Your light circuit stands on it own. It shares nothing. On and off. The brake circuit shares responsibility with the turn signal and emergency flashers. When no lights are on and you put the turn signal on, the heavy filiment will get a interupted voltage. Your license plate light is off the same circuit as the tail lights. I like to use dielectric grease on my light bulb metal bases, and any connectors like male female spade plug etc. You can get a tube at any auto parts store. It prevents corrosion and helps the metal to metal electical contact.


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## Jman (Jan 31, 2011)

i think i figured out the 4 wires. 1 is lights, 1 is brakes, 1 is license plate. cant get anything on 4th wire but i think it is reverse lights which dont work and arent a concern for now. so now that i know brakes share turn signals and hazards and i know how to test the fixture to light the correct filament for the correct reason and which wire does which function and i found enough new sockets to replace all 6 of them and i now know to grease them to prevent corrosion and promote longevity, i think i can wire this thing up and be in good shape. thank you very much for all your help dimitri. i will report back once the work is complete


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## likethat (Oct 5, 2007)

Ok Brown is your running lights aka tail lights. They come on with your head lights, Dark Green is Pass side turn signal, Yellow is Drivers side turn signal, Dark Green and Yellow combined are stop lights. As stated earlier in the thread. Light Green is back up lights, all Black wires are grounds, Tan is for the fuel tank, White wires are usually courtesy lights, dome, floor, any white lights to see with.

As wiring goes things corrode and can migrate up wires in there jackets a good distance. If you live or the car is from where they salt roads it can go feet up the wire, and you can't see the wire is bad. A good sign is that the cooper color of the wire will turn black.

Any past repair is the first place to look for something wrong as it is very prone to corrosion.

I would also say the sockets have loose connections since you stated that wiggling the wire turned on lights.
Chasing electrical trouble is tedious work, but it is like a road or a river. So just follow the colors and gauge of a wire and for the most part you will find the trouble.


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## likethat (Oct 5, 2007)

Here is a 73 Camaro wiring diagram. I googled on the Images tab "GM wiring diagram" and randomly click this one. As most GM cars from the 60's and 70's are wired the same for their light circuits. It shows how the tail lights and stop lights are wired. It also shows the color of the wire for what light it illuminates and it's function. This is the same color code as your car.


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## Jman (Jan 31, 2011)

yeah i figured out late last night that my last thought on the wiring was wrong because i was allowing for separation of the turn signals but thanks for your help and for the diagram, i have already printed it and put it with the car! found any links to a diagram for the fuse panel?


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## dimitri (Feb 13, 2009)

Jman, you are posting in the General Discussion forum. If you go to the Technical Forum for 1964-1974 Pontiac GTO at the very top there are stickies. There is a sticky that has electrical diagrams for all years. Also you should read all of the stickies in this in all three sections. It is full of great info.

Keep us posted on this project.


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## Jman (Jan 31, 2011)

cool, will do, thanks for the info. i havent spent much time navigating this site. i came here for some quick help and got it so i have been spending more time working on my car and less time researching thanks to everyones help


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## Jman (Jan 31, 2011)

ok i finally have it all working and back together and i even color matched the wiring so thanks for everyones help and i will now post my technical questions on the technical forum, so thanks again and see you there


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