67 GMC SWB-License Plate Light Wiring?

[67JimmyMO]

Anyone know how (or if?) the license plate light wire is supposed to tie in to the taillight wiring harness?

I have the flat 4-wire lead running back the driver's side frame rail to the plug behind the rear axle, then it splits to go to each taillight...but I don't see anywhere to plug in the license plate light.

Here is a pic of the light, and of the pigtail/plug end that is coming off of the light.

[Sammy]

Looked at the Assy manual. Says BRN. tracing it shows spliced to the marker lights.

[67JimmyMO]

Originally Posted by Sammy

Looked at the Assy manual. Says BRN. tracing it shows spliced to the marker lights.

Thanks for that Sammy, but this truck has no marker lights. Did any 67s have them?

[Sammy]

I assume since you don't have marker lights the brown from the RR or LR tail light are also spliced in the same harness. Yellow/green/ Lt Green are backup n brakes.

[Sammy]

I realized that I was looking at a 71 chart. It shows black lead from your Lic bulb to brown traced to a brown splice which also feeds your tail lights. Yeah, I never hook up my lic plate lights as long as the police don't bug me.

[Sammy]

Look for the brown n tie in there trace it make sure that brown feeds both tails you should be good. Stay away from the other colors..

[67JimmyMO]

Originally Posted by Sammy

Look for the brown n tie in there trace it make sure that brown feeds both tails you should be good. Stay away from the other colors..

Sounds good, will do. I was hoping I wouldn't have to cut in to the harness but not a big deal.

The last time I got stopped by the local authorities (different truck, years ago) it was for an...unlit license plate light.

[Sammy]

Checked my 69 it has reflector markers no bulbs. Confirms usage of the brown. Different style of light I have for the step bumper.

[67JimmyMO]

Maybe this bumper was installed later and never hooked in?

Were the bumpers commonly or typically installed by the dealers on these trucks?

Not sure if my bumper is original but it is definitely old...the license plate light lens has a Guide 67 on it.

[Sammy]

Mostly a dealer installed. But when my Dad bought his 69 they wanted $24 to install a $35 bumper. My Dad just had them put it in bed.
On the 67/68's over the years I have seen maybe eight or more different style step bumpers for fleet bed trucks. Narrow, wide, sorta wrap around, even thicker, some with the dealer name n City welded onto the face. So being a dealer installed item just about anything could have been installed.

[Andy4639]

Easy way to hook it up is take connector loose at rear end and put a 12 volt test light on the connections with the parking lights on only. Which ever connector lights up the test light you just found the wire to hook to. 40+ year old trucks owned by several others who may are may not of cared what color wire they used.

[A.Bursell]

There should be some piece of the original brown wire coming from the left taillight. I think most connectors were cut when an aftermarket step bumper was installed, as the factory "no-bumper" light would plug in, as well as a factory bumper light.

Once you know you have a piece of the brown wire, next step is a little bit of luck. Go to the junkyard and look for a 70's-80's van (73+ pickups will not work). They will have the same brown wire with same connector for license plate light and you will be able to cut it off back far enough to have enough wire so you can splice it back over to lead coming from your taillight.

Do a nice splice with heat shrink and you will be good as new.

Adam

[67chevy1series]

On my original 67 rear tail light wiring harness the license plate light is tied into the driver taillight wire, and judging by how the license plate light only comes on when you turn on your running lights or both headlights and taillights it's in the wiring for the taillight portion only, not the brake or turn signal wire (I forgot which color wire it is... Sorry)

[67JimmyMO]

Originally Posted by A.Bursell

There should be some piece of the original brown wire coming from the left taillight. I think most connectors were cut when an aftermarket step bumper was installed, as the factory "no-bumper" light would plug in, as well as a factory bumper light.

Once you know you have a piece of the brown wire, next step is a little bit of luck. Go to the junkyard and look for a 70's-80's van (73+ pickups will not work). They will have the same brown wire with same connector for license plate light and you will be able to cut it off back far enough to have enough wire so you can splice it back over to lead coming from your taillight.

Do a nice splice with heat shrink and you will be good as new.

Adam

I will see if I have an existing piece of brown wire coming off the left side, and great info on the 70s-80s van as to where where to find the right connector to match my existing, thanks.

This license light connection is the first instance I've found of any wiring that is missing/cut/unconnected on this whole truck, everything else appears virtually untouched.

Thanks to everyone for their input, much appreciated!