#1  
Old 05-21-2022, 05:32 PM
Michael.G Michael.G is offline
Junior Member
 
Join Date: May 2020
Posts: 3
Default 1968 GTO Rear Passenger Turn Signal

Need help with Rear Passenger Turn Signal on 1968 GTO

Problem:
Head Lights On
Brakes On
Turn Signal Clicked On for Passenger Side
Outer Bulb on Passenger Side Blinks
Inner Bulb on Passenger Side does NOT blink - it stays solid
No Issue when repeated for driver's side

Troubleshooting Done So Far
Head Lights Off
Brakes Off
Turn Signal Clicked On for Passenger Side
Outer and Inner Bulbs on Passenger Side Blink in tandem
No Issue when repeated for driver's side

Next Item Tried
Used connection wiring from Passenger Side and plugged into Driver Side
Head Lights On
Brakes On
Turn Signal Clicked on for Passenger Side
Outer Bulb on Passenger Side Blinks
Inner Bulb on Passenger Side does NOT blink - it stays solid
Was unable to switch driver side connection to passenger side.

Next Item Tried
Disconnected the grounding strap on inner passenger bulb
Sanded area and connected a wire for grounding to the socket
Went back to passenger harness connected to passenger housing
Head Lights On
Brakes On
Turn Signal Clicked on for Passenger Side
Outer Bulb on Passenger Side Blinks
Inner Bulb on Passenger Side does not blink - it stays solid
No issue when repeated for driver's side.

Next Item Tried...
Same as the last one except we removed the ground wire on the inner bulb
And now the passenger side bulbs blink but not in tandem.
The inner goes on while the outer is off. Then vice versa.

This is our last gremlin for inspection...

Any thoughts?
Michael

__________________
Michael
1968 GTO in a bunch of pieces right now!
  #2  
Old 05-21-2022, 05:58 PM
Peter Serio's Avatar
Peter Serio Peter Serio is offline
Ultimate Warrior
 
Join Date: Mar 2000
Location: Columbus, OH 43209 USA
Posts: 2,647
Default

1968 GTOs used a fiberglass molded bucket assy for the rear bumper mounted tail lamps. The sockets inside were grounded to the rear bumper which in-turn was ground to the frame of the car via the bumper mount brackets.

After many years the ground straps for the tail-lamp buckets are often rusted, broken, loose, damaged or missing. Some buckets used flat steel "straps" for the grounds and others I have seen use a flexable mesh weave very much like braided copper ground strap(s). There are 3 lamp sockets per each Left and right so the straps sometimes are not grounded well to the separate sockets. Either way I would check those first.

__________________
Peter Serio
Owner, Precision Pontiac
  #3  
Old 05-21-2022, 07:07 PM
Michael.G Michael.G is offline
Junior Member
 
Join Date: May 2020
Posts: 3
Default

Thank you for the response Peter.

We actually removed the housing, sanded the area, and then used a wire for grounding.

Same problem.

__________________
Michael
1968 GTO in a bunch of pieces right now!
  #4  
Old 05-21-2022, 09:50 PM
Peter Serio's Avatar
Peter Serio Peter Serio is offline
Ultimate Warrior
 
Join Date: Mar 2000
Location: Columbus, OH 43209 USA
Posts: 2,647
Default

Have you checked the front turn signal housing ground? Those fronts have 2 "+" wires and perhaps a ground in the plug in. I know the bulb sockets do sometimes come "un-grounded" from the steel housing as the housing gets old and water leaks inside.

Have you checked the wiring in the front where the headlamps plug-in? There should be a single black wire; one per each side, that runs off of the headlamp plug(s) and then it grounds to the core support via a ring terminal?

__________________
Peter Serio
Owner, Precision Pontiac
  #5  
Old 05-22-2022, 02:01 AM
gto4ben gto4ben is offline
Senior Member
 
Join Date: Aug 2006
Location: Los Angeles, CA
Posts: 192
Default

I performed some bench tests trying to replicate your problem.

Two possibilities:

1. The 1157 bulb is installed backwards somehow. The brake/turn signal filament is on the parking lamp circuit and the parking lamp filament is on the brake/turn signal circuit. The brake/turn signal filament is so bright that it dominates and appear solid when the headlamp switch is turned on. When the headlamp switch is OFF, you see the parking lamp filament pulsing, albeit dimmer but visible and in sync with the other bulb.

2. There may be a series resistance of 2.5 ohms in the affected socket's pigtail to the brake turn/signal filament. This will dim the pulsing to the brightness level of the parking lamp filament; however, you would see some flickering. This flickering is subtle and may look solid if ambient lighting is bright.

Hopefully it's one of these. The outer and Inner bulbs are tied in parallel and It's very limited how one can get one to behave differently from the other. I attached a wiring diagram and a chart form of your tests if it can help anyone else solve your problem.
Attached Thumbnails
Click image for larger version

Name:	troubleshooting steps.jpg
Views:	45
Size:	68.4 KB
ID:	591311   Click image for larger version

Name:	68wir5.jpg
Views:	36
Size:	42.4 KB
ID:	591312  

  #6  
Old 05-22-2022, 08:39 AM
dataway's Avatar
dataway dataway is offline
Ultimate Warrior
 
Join Date: Jan 2012
Location: Saratoga NY
Posts: 8,922
Default

Yep ... I'd swap bulbs from inner to outer to see if the problem follows the bulb.

The original sockets get pretty hinkey after five decades, sometimes you can stuff a bulb in there the wrong way and it will "fit".

__________________
I'm World's Best Hyperbolist !!
  #7  
Old 05-22-2022, 03:49 PM
Peter Serio's Avatar
Peter Serio Peter Serio is offline
Ultimate Warrior
 
Join Date: Mar 2000
Location: Columbus, OH 43209 USA
Posts: 2,647
Default

On those old real lamp sockets, probably back as far as the early 1970s GM did acknowledge that there was a problem during the car's original lifetime with 1968 and 1969 taillamp sockets and they did offer a service pack to field-repair the copper "touch" ends. The ones where there were those springs underneath.

I think I have part of one of those "kits" left here; if any interest I would post a photo. The springs can rust or get weak over time and that ends up; you think the bulb(s) are in there but one of the ends has intermittent or no contact with the car's trunk wiring harness.

__________________
Peter Serio
Owner, Precision Pontiac
  #8  
Old 05-22-2022, 06:36 PM
Michael.G Michael.G is offline
Junior Member
 
Join Date: May 2020
Posts: 3
Default

Ok... we have a winner.

We removed the light bulb turned it 180 degrees and reinstalled it.

Both now flash in tandem.

Thank you for the great troubleshooting.

Next step... inspection lanes!

And at some point body work!

Thank you!
Michael

__________________
Michael
1968 GTO in a bunch of pieces right now!
The Following User Says Thank You to Michael.G For This Useful Post:
  #9  
Old 05-22-2022, 08:15 PM
OG68's Avatar
OG68 OG68 is offline
Ultimate Warrior
 
Join Date: Dec 2011
Location: Chula Vista, CA
Posts: 1,475
Default

As mentioned by Pete
Attached Thumbnails
Click image for larger version

Name:	278DE822-F1FE-4185-85E6-FB6C972B7053_1_201_a.jpg
Views:	55
Size:	77.7 KB
ID:	591356   Click image for larger version

Name:	46DF11BA-3D52-43EB-8806-2B6C473EEC36_1_201_a.jpg
Views:	47
Size:	41.5 KB
ID:	591357   Click image for larger version

Name:	72D5A483-2033-4CD1-862B-F5A018C1DBC2_1_201_a.jpg
Views:	55
Size:	57.1 KB
ID:	591358  

__________________
Ed

1968 GTO (Thanks Mom)
2006 Silverado
2007 Cadillac SRX
2015 Chevy Express

The Following User Says Thank You to OG68 For This Useful Post:
  #10  
Old 05-23-2022, 08:13 AM
dataway's Avatar
dataway dataway is offline
Ultimate Warrior
 
Join Date: Jan 2012
Location: Saratoga NY
Posts: 8,922
Default

Cool bit of trivia there OG. You seem to have all that stuff

__________________
I'm World's Best Hyperbolist !!
The Following User Says Thank You to dataway For This Useful Post:
Reply

Thread Tools
Display Modes

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

Forum Jump


All times are GMT -4. The time now is 06:48 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017