6066 (1960-1966) GMC Truck Club Bitcoin now accepted here! 
Pay Dues
Pay Dues or become a Site Supporter

Go Back   6066 (1960-1966) GMC Truck Club > 6066 GMC Truck Club Forum > Interiors, Dash, Lights and Electrical

Interiors, Dash, Lights and Electrical Everything Inside

Thread Tools
Old July 15th, 2017, 07:05 PM
jbgroby's Avatar
jbgroby jbgroby is online now
Senior Member
Join Date: Jan 2013
Location: Lacombe, LA.
Truck: 1960 8' fleetside
Posts: 450
Rep Power: 142
jbgroby is on a distinguished road
Default Tail Light gremlin

I hope i explain this correctly and also hope other can direct me to the possible fix?

When I pull the headlight switch out to the first position the hood running light and tail lights come on. When I press the brake pedal the passenger side brightens but NOT the drivers side.

BUT when I pull the switch to out fully to turn on the head lights, the tail light out out?

Any pointers?
21 circuit from E-Z wiring is what is installed

Reply With Quote
Old July 15th, 2017, 08:18 PM
AZKen AZKen is online now
-= Dues Paid =-
Join Date: Jul 2014
Location: State48
Truck: 1960 K1001 Wideside 305 BW Custom Cab
Posts: 747
Rep Power: 0
AZKen is infamous around these partsAZKen is infamous around these parts
Default Re: Tail Light gremlin

You would first want to switch rear bulbs and see if the problem follows the bulb. Also, on the one that won't light, stick a temporary ground from bulb socket to a good ground at rear while applying brakes. Report what happens.

Then: All I can say is re check the circuits once you know how it's supposed to be wired. The stop switch has a hot-all-the-time wire on one terminal and a wire that goes to the turn signal switch from the other terminal. Then two other wires come out of the turn signal switch. One for left brake/turn and one for right brake.turn. If you check at various connections/connectors/terminal blocks with a 12V ice pick tester light. that way you can see if 12V is present all the way back to tail light. (of course, be sure brake pedal is applied during all this). Take out the bulbs and touch the proper contact inside the socket with the probe and attach it's wire lead to a good ground back there. See if you can get both left and right to light the test light with brake applied. If that works, then it's the bulb or the socket is not grounding. If one does not light still, follow the wire for that bulb back until you find power. Report what happens.

I would like to know if the rear turn signals work?
You have a dual filament bulb back there. The rear running light "filaments" are wired to the headlight switch. The turn/brake filaments are wired to the turn signal. Don't get that mixed up. Follow the 1960 Diagram, the EZ wire instructions are generic. Don't let colors fool you, be sure the hook up is correct functionally.

Could be a simple ground problem or bad bulb.
Could be headlight sw not wired correctly, turn signal sw not wired correctly, or other wiring. The tests and wire checks above will start to tell.

Last edited by AZKen; July 15th, 2017 at 10:23 PM.
Reply With Quote
Old July 16th, 2017, 11:38 AM
James James is offline
Tinkering on old trucks.
Join Date: Jun 2013
Location: Greer, SC
Truck: 1964 GMC 1500 2wd
Age: 62
Posts: 86
Rep Power: 48
James is on a distinguished road
Default Re: Tail Light gremlin

Originally Posted by jbgroby View Post
BUT when I pull the switch to out fully to turn on the head lights, the tail light out?
For this to happen I would suspect the headlight switch. Are you stepping on the brake when you turn on the headlight? Did the brake lights work when the headlight switch all of the way in?
Reply With Quote
Old July 17th, 2017, 06:14 PM
ilvracn's Avatar
ilvracn ilvracn is offline
-= Dues Paid =-
Join Date: Nov 2013
Location: atlantic iowa
Truck: 1966 gmc 1500
Age: 52
Posts: 111
Rep Power: 51
ilvracn is on a distinguished road
Default Re: Tail Light gremlin

sounds like you are losing ground to rear light. sockets go bad.ground is back feeding. my 66 did the same thing, i was able to temporarly get connection, by cleaning and wiggling bulb. did this numerous times. got tired of people telling my brake light wasn't working on one side. i installed led replacements. they come as a whole light. you will need to cut the socket off of the new light, they are made to go in place of the bulb, but that will not fix your problem, if you don't eliminate the bulb socket. i ordered them from cpp or tuckers, can't remember. have had no problems since
Reply With Quote


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tail light question Archiver Previous Forum Posts 0 October 21st, 2009 01:53 AM
Re: Tail light question Archiver Previous Forum Posts 0 October 21st, 2009 01:49 AM
Tail And Brake light wiring???? Archiver Previous Forum Posts 0 September 27th, 2009 01:21 AM
Re: Suburban Tail LIght Assembly Archiver Previous Forum Posts 0 September 2nd, 2009 01:51 AM
Original Tail Light Lense? Archiver Previous Forum Posts 0 December 23rd, 2001 12:38 AM

All times are GMT +1. The time now is 04:21 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2013, Jelsoft Enterprises Ltd 125|0
Feedback Buttons provided by Advanced Post Thanks / Like (Lite) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.