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Old 03-17-2018, 02:54 PM   #1
Project86
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Ez wiring harness to 86 factory tail light harness HELP!!

Finishing up the wiring on my 86 c10

I'm using the ez wiring harness.
My truck has the taillight harness with a four wire plug

No matter how I connect any of the wires. My brake lights will not light up.

I was told I had to splice directly to the bulb sockets. But I would prefer to keep the original harness.

Has anyone ran into this same problem?
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Old 03-18-2018, 09:46 AM   #2
phat69
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Sounds like a ground issue. Do you own a power probe?
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Old 03-18-2018, 10:44 AM   #3
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

If you are referring to the rubber 4-wire mating plugs-those are obsolete and nobody reproduced them-this is why I use weatherpack 4-cavity square connectors on my lighting harnesses. You have to combine the grounds to a single grounding ring and the rear lighting circuit grounds to the body behind the tail light housings. And, your box should have a grounding strap from a floor support brace to the frame as well.
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Old 03-19-2018, 09:00 AM   #4
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

All the grounds are in place in the factory locations. And the four wire connector is a weatherpac type connector

There's a yellow, brown, light green and a dark green

The new harness has yellow, green, brown and orange.
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Old 03-19-2018, 09:33 AM   #5
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Yellow and dark green are your turn signal +12V leads, brown is spliced to all other browns and light green is your backup +12 lead. Orange is NOT part of GMs’ tail light wiring schematic that I’m aware of. Are the black leads from the turn signal socket going to chassis ground then?
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Old 03-19-2018, 03:12 PM   #6
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Alright that clarified things a bit. I'll give it a shot again tonight and post back with the results
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Old 03-19-2018, 03:25 PM   #7
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Quote:
Originally Posted by gmachinz View Post
Yellow and dark green are your turn signal +12V leads, brown is spliced to all other browns and light green is your backup +12 lead. Orange is NOT part of GMs’ tail light wiring schematic that I’m aware of. Are the black leads from the turn signal socket going to chassis ground then?

Here's a couple of diagrams that show the wiring of the turn signal switch and they also don't show an orange wire. There are additional wires added for the courtesy light and key in buzzer, but the main wiring is the same as it was back in the sixties.

86Chevy

Name:  86 chevy.jpg
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another 86 chevy

Name:  86 chevy 2.jpg
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Size:  74.6 KB



and here's an 88 diagram.


Name:  88 wiring diagram.gif 2.jpg
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Size:  82.9 KB


The new harness may have the orange wire as a substitute but it should be stated as to what it is.
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Old 03-20-2018, 05:37 AM   #8
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Quote:
Originally Posted by VetteVet View Post
Here's a couple of diagrams that show the wiring of the turn signal switch and they also don't show an orange wire. There are additional wires added for the courtesy light and key in buzzer, but the main wiring is the same as it was back in the sixties.

86Chevy

Attachment 1765015


another 86 chevy

Attachment 1765016



and here's an 88 diagram.


Attachment 1765018


The new harness may have the orange wire as a substitute but it should be stated as to what it is.

I did forget to mention the orange wire is for the third brake light. Since I don't have one, I can just tape it up and leave it within the harness

I don't have any dome lights or courtesy lights anymore as well so it helps simplify things a bit.

I haven't had a change to tinker with it but I'm hoping to have everything finished up soon
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Old 03-26-2018, 07:49 AM   #9
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Little update. Rear lights work now. As well as brake lights. However the driver side lights seem a lot dimmer than the passenger side
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Old 03-29-2018, 01:21 AM   #10
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Bump. Tinkered around with the tail lights.
I now no tail running lights. Brake lights work, however driver side lights are dimmer than the other

Turn signals world but same thing with being dimmer than the passenger side.

I'm completely lost.
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Old 03-29-2018, 09:10 AM   #11
gmachinz
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

At this point I’m willing to bet you’ve got excessive resistance due to corrosion within the wire jacketing itself-common problem with “customer” added trailer harnesses prior to you owning the truck.
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Old 03-29-2018, 09:28 AM   #12
Project86
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Quote:
Originally Posted by gmachinz View Post
At this point I’m willing to bet you’ve got excessive resistance due to corrosion within the wire jacketing itself-common problem with “customer” added trailer harnesses prior to you owning the truck.
I did not even think of that honestly

I tinkered around with the lights this morning. I made a separate thread about it.

When my switch is pulled out to the first detent for parking lights everything works

Then I pull the switch all the way out and I have no tail lights. But the turn signals still work.
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Old 03-29-2018, 10:10 AM   #13
gmachinz
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Did you check both grounding rings behind LH and RH tail light lenses? Use a test light and verify voltage on the brown wire in the 4-wire firewall bulkhead connector-if its good, go check any brown wire at the rear-this is the power wire for the running lights. After this we can troubleshoot the ground circuit.
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Old 03-29-2018, 11:37 AM   #14
Project86
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Ok just used a test light connected to a ground on the driver taillight housing.

Test light didn't light up at all. The two brown wires are labeled right tail park and left tail park. And there's a short one for the license playe
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Old 03-29-2018, 11:45 AM   #15
Project86
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

No power coming out of the dark purple and brown wire off my new headlight switch I just put in.
When we did the headlight switch portion of the wiring we jumped the purple and brown together. And those to go to the two brown wires are labeled as left front park. And left tail park
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Old 03-29-2018, 05:16 PM   #16
Project86
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Re: Ez wiring harness to 86 factory tail light harness HELP!!

Alright guys thanks for all the good info!
I ended up calling EZ wiring and within 2 minutes of being in the phone I had taillights

For anyone having any type of issues, at the headlight 7 pin switch, you need a jumper from the switch power, to any of the orange wires.

Made the jumper and everything works fine
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