brake light wiring help, lost em - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sactoC10 · 11-09-2003, 01:35 PM

OK, yesterday I removed the trailer wiring that had been spliced into my taillights. I simply removed the soldered portion and re connected the wires. After doing so, the turn signals worked, but the brake lights stopped working. Can't figure out what changed and need to get these fixed ASAP. Any ideas?

The splice was done in the taillight wiring section, right near where it plugs in by the frame. The extra set of wires had one lead that was attached near the voltatge regulator, maybe this is the missing link?

I can't figure it out because I'd think that the wires out of the harness are all simply green to green, light green to light green, purple to purple, etc... HELP!

Thanks in advance.
JT

jef5150 · 11-09-2003, 01:40 PM

heres a pic,,,,,,,,,,,,,jeff

ChevLoRay · 11-09-2003, 01:48 PM

If we are gonna drive old trucks, we have to have a test light. You can use it to "find" the wire that is what you want it to be, i.e., the brake light, or turn signal, etc. It will take a buddy to hit the brake pedal, but you can do yourself a lot of good by using the test light. You'll be glad you did.

Only other answer is to buy a new harness. I know they aren't cheap, but you gotta figure how much your truck is worth. 30+ year old wiring is not gonna last forever. Replacement harnesses are color-coded to be correct. One source is: www.wiringharness.com
They build all the harnesses that Early Classic Enterprises sells. But, they will build and sell to us, too.

jef5150 · 11-09-2003, 01:48 PM

heres a link for all wiring diagrams http://www.rayschevy.com/images/guid...ms/diagram.htm jeff

Longhorn Man · 11-09-2003, 06:50 PM

The problem is not going to be in the chassis harness.
Your turn signals work, and the turn signals use the same wires that your brake lights use. (Yellow on one side and green on the other)
Your problem is going to be somewhere inbetween the turn signal switch, and the brake pedal. (asuming the fuse was checked...I can't remember if the turn signals use the same fuse.

JimKshortstep4x4 · 11-09-2003, 08:49 PM

Longhorn is right, the turn signals and brake lights use the same wiring going to the rear. The turn signal fuse is separate from the brake light fuse. If it is not the brake light fuse, then I would check the brake light switch.

Jim

72shadetree · 11-10-2003, 12:47 AM

are you sure the signals and brakes dont use same fuse ive got a short and keep blowing one fuse when the fuse blows i lose signals/brakes and taillights

sactoC10 · 11-10-2003, 02:11 AM

OK, the diagram is good and helps much, as does all the information. But remember, everything worked fine before I removed the nasty old trailer wires, so why would it suddenly be related to the switch or the pedal?

I'm thinking that maybe I ought to get in there again and simply cut the splices cleaner and re-attach everything, since it does appear that the brake lights/tail lights, signals etc should all be working.

I do have a test light. Where is the switch for the brakes, just in case I end up having to check that out? Thanks, it is simply a bummer.

Longhorn Man · 11-10-2003, 02:18 AM

The switch is above the brake pedal. The arm that holds the foot pad activates it.
You're wastin your time by re-splicing it.

Cat Fuzz · 11-10-2003, 02:19 AM

Check your grounds. The taillight housing are grounded when you bolt them in, if its rusty back there, like mine were, you need to clean it up or run a ground wire from the housings to the body. The old trailer wiring may have been providing the ground in place of the original ground.

Longhorn Man · 11-10-2003, 02:26 AM

Naaa, his turn signals wouldn't work with a bad ground.

A.P. · 11-10-2003, 03:20 AM

To my experience the fuse for the brakes is seperate from the turn signal. But if your not sure, just remove the fuse and turn on the turn signal. I'll go check on my truck.

A.P. · 11-10-2003, 03:36 AM

O.K. I removed the brake fuse and turned the turn signals on. Turn signals still work without the brake fuse.
SactoC10 check on the fuse for the brakes if there is 12V.

sactoC10 · 11-10-2003, 12:04 PM

OK I'll check it today. Another question. Wouldn't one specific wire be the one to send the signal to the brakes? If I were using the test light, that's the one I'm looking for. So then that would be the one that may be the problem, no?

Suicide-D · 11-10-2003, 12:34 PM

I just replaced my turn signal switch because I had no brake lights...I followed the juice all the way in to the turn signal but not out. I had a wire in the tailight harness that was shorting to ground and popping fuses I think it burned up my turn signal switch because it worked fine before hand. Everything works now that I fixed both.

sactoC10 · 11-10-2003, 03:52 PM

According to that wiring diagram, it may be the brown wire that is common to both, the one that I'd referred to as purple. Hmmm...
OK- test light , check grounds , check fuse , switch , re-check wires... good late afternoon/evening activity!

Longhorn Man · 11-10-2003, 05:39 PM

Nope, the brown is for the parking lights.

sactoC10 · 11-10-2003, 06:32 PM

I'm looking at something here. I see that the license plate ground comes off of the brown leads that extend to the tail lights. If that license plate ground is not grounded, could that cause a tail light problem? I was thinking that I did not try my "lights" as in the tail lights along with the head lights.

Any thoughts about that ground?

JimKshortstep4x4 · 11-10-2003, 09:58 PM

The brown wire at the license plate is the hot wire for the bulb. The bulb gets its ground through the bumper which bolts to the frame, etc.. The brown wire that goes to the license plate light is tied into both taillights and those wires are brown. There are no ground wires in the factory front to rear wiring.

Your brake light problem has to be up front as the turn signals are working.

Jim

Andy4639 · 11-11-2003, 11:59 PM

Have you taken the plug loose at the rear connector and tested all the wires there? Right under the frame at the rear of the truck is a rubber plug that comes apart. Take it apart and test all of those wires with a test light to see if they work. If they do than you know it's in the wiring from there on back. You will need a person to do this for the brakes or do like I did and make a 2x4 that will hold the brake pedal on while you are under the truck. Check all the terminals at that connection and that will narrow it down a lot. Hope this helps.

sactoC10 · 11-12-2003, 12:33 AM

Well, I went and picked up my roll pan today...had to take a short jaunt to get it and save on the shipping. Also hunted down some other spare parts, but due to some family matters (crisis after crisis) I was unable to check any of this, probably tomorrow or the next day. Keep the input coming!

Longhorn Man · 11-12-2003, 01:00 AM

Andy4639, the problem won't be back in that plug either. The power is getting to each terminal on each light through all 3 wires. So therefor, there is no way it can be under the truck, every wire is doing its job.
I will bet you my next paycheck (60+ hrs) that the problem will be in the cab.

On second thought, my wife would beat the ca-ca out of me just for saying that...she insists that I only bet a punch in the gut...so I guess I'll bet a punch in the gut.

11-09-2003, 01:35 PM	#1
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,056	brake light wiring help, lost em OK, yesterday I removed the trailer wiring that had been spliced into my taillights. I simply removed the soldered portion and re connected the wires. After doing so, the turn signals worked, but the brake lights stopped working. Can't figure out what changed and need to get these fixed ASAP. Any ideas? The splice was done in the taillight wiring section, right near where it plugs in by the frame. The extra set of wires had one lead that was attached near the voltatge regulator, maybe this is the missing link? I can't figure it out because I'd think that the wires out of the harness are all simply green to green, light green to light green, purple to purple, etc... HELP! Thanks in advance. JT Last edited by sactoC10; 11-10-2003 at 02:03 AM.

11-09-2003, 01:40 PM	#2
jef5150 Inline 69 Join Date: Apr 2003 Location: valleysprings,california Posts: 1,018	rear diagram heres a pic,,,,,,,,,,,,,jeff Attached Images

11-09-2003, 01:48 PM	#3
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	....Buy a Test Light! If we are gonna drive old trucks, we have to have a test light. You can use it to "find" the wire that is what you want it to be, i.e., the brake light, or turn signal, etc. It will take a buddy to hit the brake pedal, but you can do yourself a lot of good by using the test light. You'll be glad you did. Only other answer is to buy a new harness. I know they aren't cheap, but you gotta figure how much your truck is worth. 30+ year old wiring is not gonna last forever. Replacement harnesses are color-coded to be correct. One source is: www.wiringharness.com They build all the harnesses that Early Classic Enterprises sells. But, they will build and sell to us, too. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

11-10-2003, 12:47 AM	#7
72shadetree KEEP ON TRUCKING Join Date: Sep 2000 Location: martinsville va Posts: 2,563	are you sure the signals and brakes dont use same fuse ive got a short and keep blowing one fuse when the fuse blows i lose signals/brakes and taillights __________________ 72 cheyenne 2wd lwb 71 k20 sons bassett va

11-10-2003, 06:32 PM	#18
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,056	wiring diagram, lp ground I'm looking at something here. I see that the license plate ground comes off of the brown leads that extend to the tail lights. If that license plate ground is not grounded, could that cause a tail light problem? I was thinking that I did not try my "lights" as in the tail lights along with the head lights. Any thoughts about that ground?

11-09-2003, 06:50 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	The problem is not going to be in the chassis harness. Your turn signals work, and the turn signals use the same wires that your brake lights use. (Yellow on one side and green on the other) Your problem is going to be somewhere inbetween the turn signal switch, and the brake pedal. (asuming the fuse was checked...I can't remember if the turn signals use the same fuse.

11-09-2003, 08:49 PM	#6
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Longhorn is right, the turn signals and brake lights use the same wiring going to the rear. The turn signal fuse is separate from the brake light fuse. If it is not the brake light fuse, then I would check the brake light switch. Jim

11-10-2003, 02:11 AM	#8
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,056	OK, the diagram is good and helps much, as does all the information. But remember, everything worked fine before I removed the nasty old trailer wires, so why would it suddenly be related to the switch or the pedal? I'm thinking that maybe I ought to get in there again and simply cut the splices cleaner and re-attach everything, since it does appear that the brake lights/tail lights, signals etc should all be working. I do have a test light. Where is the switch for the brakes, just in case I end up having to check that out? Thanks, it is simply a bummer.

11-10-2003, 02:18 AM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	The switch is above the brake pedal. The arm that holds the foot pad activates it. You're wastin your time by re-splicing it.

11-10-2003, 02:19 AM	#10
Cat Fuzz My son, my joy. Join Date: Sep 2003 Location: Spokane WA Posts: 463	Check your grounds. The taillight housing are grounded when you bolt them in, if its rusty back there, like mine were, you need to clean it up or run a ground wire from the housings to the body. The old trailer wiring may have been providing the ground in place of the original ground.

11-10-2003, 02:26 AM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Naaa, his turn signals wouldn't work with a bad ground.

11-10-2003, 03:20 AM	#12
A.P. Black 72 Chevy Join Date: May 2002 Location: Los Angeles, California Posts: 662	To my experience the fuse for the brakes is seperate from the turn signal. But if your not sure, just remove the fuse and turn on the turn signal. I'll go check on my truck.

11-10-2003, 03:36 AM	#13
A.P. Black 72 Chevy Join Date: May 2002 Location: Los Angeles, California Posts: 662	O.K. I removed the brake fuse and turned the turn signals on. Turn signals still work without the brake fuse. SactoC10 check on the fuse for the brakes if there is 12V.

11-10-2003, 12:04 PM	#14
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,056	OK I'll check it today. Another question. Wouldn't one specific wire be the one to send the signal to the brakes? If I were using the test light, that's the one I'm looking for. So then that would be the one that may be the problem, no?

11-10-2003, 12:34 PM	#15
Suicide-D Registered User Join Date: Jan 2001 Location: Katy, TX...but the love of my life resides in Dublin,OH. Posts: 1,408	I just replaced my turn signal switch because I had no brake lights...I followed the juice all the way in to the turn signal but not out. I had a wire in the tailight harness that was shorting to ground and popping fuses I think it burned up my turn signal switch because it worked fine before hand. Everything works now that I fixed both.



Register or Log In To remove these advertisements.

11-10-2003, 03:52 PM	#16
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,056	According to that wiring diagram, it may be the brown wire that is common to both, the one that I'd referred to as purple. Hmmm... OK- test light , check grounds , check fuse , switch , re-check wires... good late afternoon/evening activity!

11-10-2003, 05:39 PM	#17
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Nope, the brown is for the parking lights.

11-10-2003, 09:58 PM	#19
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	The brown wire at the license plate is the hot wire for the bulb. The bulb gets its ground through the bumper which bolts to the frame, etc.. The brown wire that goes to the license plate light is tied into both taillights and those wires are brown. There are no ground wires in the factory front to rear wiring. Your brake light problem has to be up front as the turn signals are working. Jim

11-11-2003, 11:59 PM	#20
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Wiring? Have you taken the plug loose at the rear connector and tested all the wires there? Right under the frame at the rear of the truck is a rubber plug that comes apart. Take it apart and test all of those wires with a test light to see if they work. If they do than you know it's in the wiring from there on back. You will need a person to do this for the brakes or do like I did and make a 2x4 that will hold the brake pedal on while you are under the truck. Check all the terminals at that connection and that will narrow it down a lot. Hope this helps. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

11-12-2003, 12:33 AM	#21
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,056	Well, I went and picked up my roll pan today...had to take a short jaunt to get it and save on the shipping. Also hunted down some other spare parts, but due to some family matters (crisis after crisis) I was unable to check any of this, probably tomorrow or the next day. Keep the input coming!

11-12-2003, 01:00 AM	#22
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Andy4639, the problem won't be back in that plug either. The power is getting to each terminal on each light through all 3 wires. So therefor, there is no way it can be under the truck, every wire is doing its job. I will bet you my next paycheck (60+ hrs) that the problem will be in the cab. On second thought, my wife would beat the ca-ca out of me just for saying that...she insists that I only bet a punch in the gut...so I guess I'll bet a punch in the gut.

Register or Log In To remove these advertisements.