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Old 10-14-2018, 10:52 PM   #1
HIGHWAY BY THE SEA
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Rear lights wiring harness issue

I recently bought a used wiring harness for the inoperable rear lights in my 67 3500 one-ton to replace the shoddy wiring that did not work anyway. The existing firewall male plug has three blades three wires and a slit for a fourth (backup light with light green wire) The female plug has four wires. I CANNOT seem to get any power to the rear lights from this setup. I checked the wires for continuity and they work. Do the front signal lights have to be installed and hooked up before the rear ones work? I do not have my front ones hooked up yet so I was not sure.
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Old 10-16-2018, 05:58 PM   #2
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Re: Rear lights wiring harness issue

This issue is driving me bats! I can find no reason for the rear lights wires to not have any power. My light switch is brand new.
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Old 10-16-2018, 06:27 PM   #3
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Re: Rear lights wiring harness issue

Shouldn't make a difference if they are in at the front for the back to work (I could be wrong). I would check the fuses for the lights and then work to see if there is power coming out of the switch. All else could be bad connections/wiring or missing grounds.

Smitty
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Old 10-16-2018, 09:56 PM   #4
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Re: Rear lights wiring harness issue

Removed the fuse box and checked the wires behind it. They all seem good. For some reason my gauge lights have stopped working. I checked the fuse for gauge lights, and it is good. This issue is very well hidden...
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Old 10-16-2018, 10:02 PM   #5
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Re: Rear lights wiring harness issue

Sounds like some grounds are missing. I feel your pain. Working on a Mutt Truck at the moment the the PO should have never been allowed to own tools.....Get the wiring schematic and chase it down.

Smitty
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72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber...Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378

72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one.....Gen 5 5.3/6L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110

68 Suburban was 3/4 ton, now 1/2....Wife shook her head...

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Old 10-17-2018, 06:10 AM   #6
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Re: Rear lights wiring harness issue

http://outintheshop.com/faq/wiring/w...s/image002.jpg

http://outintheshop.com/faq/wiring/w...s/image003.jpg

Time to get a test light and trace it from the light to the battery and figure out where it stops working.
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Old 10-17-2018, 06:30 AM   #7
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Question Re: Rear lights wiring harness issue

All lights come out of the turn signal. Check it first. The fire wall connector put a test light in it and check it.
Where are you on the coast? I have a place in SC in Garden City.
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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.
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Old 10-17-2018, 11:23 AM   #8
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Re: Rear lights wiring harness issue

Quote:
Originally Posted by Andy4639 View Post
All lights come out of the turn signal. Check it first. The fire wall connector put a test light in it and check it.
Where are you on the coast? I have a place in SC in Garden City.
I live in the Summerville/Ladson area 20 miles from Charleston (used to live in Charleston)..
The turn signal is probably the ONLY thing I have not checked yet. If you look at the pictures on my New Project signature you will see that the steering column is not 67 period. I think it is late 70s early 80s. I need to figure out what year it is to replace it if necessary.
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http://67-72chevytrucks.com/vboard/s...d.php?t=770578

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Old 10-17-2018, 11:41 AM   #9
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Thumbs up Re: Rear lights wiring harness issue

I'm about a 1hr north of you on 17.

Looks like a 73 up steering wheel. Look under the dash for the horse shoe connector are the flat connector where all the wires come out of the steering wheel. Check those with a test light. See if you have signals and stop lights there.
Look at the link and follow the wires to make sure they are all right.



http://67-72chevytrucks.com/vboard/s...185856&page=16
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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.
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Old 10-18-2018, 01:02 PM   #10
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Re: Rear lights wiring harness issue

First snow last night wish I was back in the SC.
Mine turned out to be rotten wire. I replaced all the wire from the three prong back and all is good now.
Good luck
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Old 10-18-2018, 06:47 PM   #11
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Re: Rear lights wiring harness issue

Measure at the cab connector to ground on each terminal when the corresponding light should be lit. Then you know if it's in the cab or not.
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Old 10-20-2018, 10:52 AM   #12
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Re: Rear lights wiring harness issue

Thanks for all the good advice gentlemen. The OEM rear light wire I ordered just came in. Here is a picture of the old one on the left and the newer one on the right. Notice that the old one lacks a reverse lights blade for some strange reason.
I was going to remove the steering wheel to remove the old turn switch to have it replaced, but since we moved I cannot find my steering wheel puller. Still looking...
After exhausting going over the wiring and diagrams for several months, I guess the problem MUST be in the turn switch. Updates later...

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http://67-72chevytrucks.com/vboard/s...d.php?t=584617
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1967 GMC 3500 dually one-ton flatbed
http://67-72chevytrucks.com/vboard/s...d.php?t=770578

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Old 10-20-2018, 12:17 PM   #13
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Re: Rear lights wiring harness issue

Before you get too excited about pulling the turn signal switch you should check the three wires that power it. On the column the connector has a white, purple and brown wire all from the fuse panel. The white is for the brakes, the purple is for the turn signals and the brown is for the hazards.

The brown wire has power full time, the white is the powered when you step on the brake pedal, and the purple is powered when the key is on.

The tail and front parking lights are powered by a brown wire off the headlight switch, but it goes to the rear harness for the tail and license plate lights.

If you get power on these wires then you can check the turn signal switch for continuity with an ohm meter.

on the harness going up the column to the TS switch check

The white wire to the yellow and dark green wire for zero ohms.

The hazard wire, usually brown, to the yellow, dark green, light blue and dark blue wires for zero ohms. With the hazard switch pulled.

If you want to check the turn signal wiring do the following

Check the purple wire to the light blue and yellow wires to the purple wire with the TS lever in left turn. Hazard switch pushed in.

Check the dark green and dark blue wires to the purple wire for zero ohms with the TS lever in the right turn position.

Sometimes the wire colors do not match but they are almost always in the same positions.

On one end you have the black horn button ground wire.
Next to it is the left turn,light blue wire,
next is the dark blue right turn wire.
then the brown hazard wire.
then the purple wire for the L and R turns.
then the yellow wire for the left turn
Then the dark green wire for the right turn,
and finally the white wire for the brake lights.


I'll double check these and post the diagram.


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Old 01-10-2019, 05:21 PM   #14
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Re: Rear lights wiring harness issue

Thanks to Vette for the comprehensive wiring post
I bought a new steering wheel puller, removed the old turn signal switch, and installed the new AC Delco turn signal switch. Still no power to the rear lights, and the cab light still does not work either, even with a new headlight switch. The old turn signal switch apparently had a short in it, because if the TSS flasher was in the fuse block, the left gauge turn indicator stayed on (not blinking). It no longer does this, but I am still at Square One for figuring out the rear wiring issue. I am further handicapped since I do not have a decent working voltmeter. I guess I will have to borrow one.
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1981 Chevrolet C10 Deluxe Shortbed Stepside
GRANDTRUCK
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http://67-72chevytrucks.com/vboard/s...d.php?t=584617
NEW PROJECT
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http://67-72chevytrucks.com/vboard/s...d.php?t=770578
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Old 01-11-2019, 07:43 AM   #15
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Thumbs up Re: Rear lights wiring harness issue

Hook everything up and check all the fuses in the block. Make sure they are all good by pulling them out and inspecting them. Not just looking at them. If they have sat for a long time they want make contact even though they should. Take each one out and reinstall.

Then go to the rear of the truck with the lights on. Pull the connector on the drivers side frame rail under the truck and see if there is power. If not go back toward the fuse panel and check the fuses to make sure your getting power. Follow the wiring all the way up to the motor checking for a break in it. If it's been pinched by a bracket are something.
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Seeing the USA in a 71


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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.
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Old 01-11-2019, 08:25 AM   #16
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Re: Rear lights wiring harness issue

Check and fix all grounding wires. Im going thru this with my 71 I just bought. Same issues as you. I added and fixed all grounds.

I used my Dremel to clean to the bare metal all my grounding straps. I added a battery cable from the engine block to the frame. I added a no.#6 gauge ground wire from the rear of the bed to the frame, using copper wire mounting lugs. Fixed grounding from cab to frame under the passenger side door.

You may have to clean the bulb connections in the rear where the bulb goes into. clean the brass and the two lead dots the bulb touches.

I have lights now.
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Old 04-12-2019, 10:06 PM   #17
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Re: Rear lights wiring harness issue

This electrical issue still has not been fixed yet due to me concentrating on other things with this truck. It is coming along overall well in other areas, but I cannot believe how many electrical problems that have popped up.
I lost all dash lights after I got them working so well (even the heater switch light), the horn never worked with the horn button; only with a "jumper", and now it does not even work with that. Still no signal lights, brake lights, inner-cab light, or license plate light. At least I got the cigarette lighter and plug fully operational so that I can charge my cell while working on it outside.
I am SERIOUSLY considering replacing the entire fuse box since there is visible rust on the metal contacts. The wires all seem OK though. I have just about decided to have a professional mechanic fix this issue, because I have gotten NOWHERE, and am sick and tired of dealing with it.
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GRANDTRUCK
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http://67-72chevytrucks.com/vboard/s...d.php?t=584617
NEW PROJECT
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http://67-72chevytrucks.com/vboard/s...d.php?t=770578
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Old 04-12-2019, 11:15 PM   #18
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Re: Rear lights wiring harness issue

Not much to the wiring systems of these trucks, if your ready to pay someone to repair would you not be further ahead and have a sense of accomplishment by installing a complete new harness yourself from one of the many companies that produce them?
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Old 04-12-2019, 11:18 PM   #19
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Re: Rear lights wiring harness issue

Quote:
Originally Posted by Bonestock3ott View Post
Not much to the wiring systems of these trucks, if your ready to pay someone to repair would you not be further ahead and have a sense of accomplishment by installing a complete new harness from one of the many companies that produce them?
I have certainly considered that, but the sheer PRICE of those new wiring harnesses is probably more than a mechanic would charge for fixing it.
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1981 Chevrolet C10 Deluxe Shortbed Stepside
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http://67-72chevytrucks.com/vboard/s...d.php?t=584617
NEW PROJECT
1967 GMC 3500 dually one-ton flatbed
http://67-72chevytrucks.com/vboard/s...d.php?t=770578
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Old 04-12-2019, 11:54 PM   #20
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Re: Rear lights wiring harness issue

So a quick search shows a complete harness for about $540 . Around me with labor rates between $85 to $100 per hour, I think I would have that amount into having an old problem prone electrical system repaired. I think it would be money well spent on the harness and investing a couple of days installing the harness myself. Just my opinion. Good luck however you choose to fix . Price www.tuckersparts.com

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Old 04-22-2019, 06:04 PM   #21
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Re: Rear lights wiring harness issue

The price of a new harness is piece of mind your truck does not burn down from 50 years of wear and tear and improper repairs done over the decades

crimp splices , wires twisted and tapped together are not as good as heat shrink and a clean solder joint for connections

Lack of clean grounding is most likely part of your issues others have mentioned it before me

Brothers and other places have Nos style harness kits buy the pieces you need today and buy other parts as needed

the fit factory harness like the originals did

https://www.brotherstrucks.com/69-72...tinfo/WH22075/
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Old 04-22-2019, 06:20 PM   #22
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Re: Rear lights wiring harness issue

Quote:
Originally Posted by gmc684x4 View Post
The price of a new harness is piece of mind your truck does not burn down from 50 years of wear and tear and improper repairs done over the decades

crimp splices , wires twisted and tapped together are not as good as heat shrink and a clean solder joint for connections

Lack of clean grounding is most likely part of your issues others have mentioned it before me

Brothers and other places have Nos style harness kits buy the pieces you need today and buy other parts as needed

the fit factory harness like the originals did

https://www.brotherstrucks.com/69-72...tinfo/WH22075/
Thanks for the assist!! The problem has been fixed though! See the New Project link in my signature (pages 4-5) for all the details!
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1981 Chevrolet C10 Deluxe Shortbed Stepside
GRANDTRUCK
1968 Chevrolet C10 Stepside Longbed
http://67-72chevytrucks.com/vboard/s...d.php?t=584617
NEW PROJECT
1967 GMC 3500 dually one-ton flatbed
http://67-72chevytrucks.com/vboard/s...d.php?t=770578
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