[torqhead]

On my 69 GTO I replaced the rear sockets with 3 wire versions about 5 years ago. Recently, the left rear tail lights when brake or turn are dim, as if they are missing the ground, ie where the parking light filament lighting versus the brake filament in the 1157 bulb. Even if I take a good known ground from the body body to the outside body of the bulb when it is in the socket makes no difference.

The right tail light is fine. Is there any change the turn signal assembly has gone bad and possibly causing this problem. The turn signal work for both direction but the left is dim for the same above reason. I've tested with no bulbs installed and validated the sockets have proper ground and they get +12 volts on the correct pins for both parking light and brake/turn. Sockets are still like brand new. .

["QUICK-SILVER"]

Bi-metal flasher or transistorized? With bi-metal flasher the blink rate should be slower if there's high resistance in the turn signal switch. That's left turn compared to right turn.

Does hazard/emergency flasher have the same problem on left rear?

Could use a jumper wire at the turn signal switch connector to by-pass the turn signal switch and see if bulb intensity comes back. If the jumper doesn't restore brightness... Something is wrong in the back or wires going back there.

Need to get this isolated before you start scratching your head
Clay

[torqhead]

Originally Posted by "QUICK-SILVER"

Bi-metal flasher or transistorized? With bi-metal flasher the blink rate should be slower if there's high resistance in the turn signal switch. That's left turn compared to right turn.

Does hazard/emergency flasher have the same problem on left rear?

Could use a jumper wire at the turn signal switch connector to by-pass the turn signal switch and see if bulb intensity comes back. If the jumper doesn't restore brightness... Something is wrong in the back or wires going back there.

Need to get this isolated before you start scratching your head
Clay

Heya Clay, I'm already scratching my head... lol It's the original flasher and yes it does flash slower (worse with parking lights on) which makes sense. When I converted the sockets I soldered all the wires back there and made sure it was a good solid clean install. One other data point I forgot to mention if I have the reverse light bulb in and it's plugged in (getting it's ground from the factory setup) the reverse light will come on really dim too on that same side which tells me the power is traversing through that ground point (same ground that the turn signal bulbs are connected to on the tail light housing).

["QUICK-SILVER"]

Flash speed slower with parking lights and back-up light glowing...

Time to double check those ground wires and connections


"(same ground that the turn signal bulbs are connected to on the tail light housing)".

That last line would indicate the tail lamp housing isn't grounded. Could check it for a presence of voltage with lights on and then fix or add a good ground wire to the body.

Clay

[torqhead]

Originally Posted by "QUICK-SILVER"

Flash speed slower with parking lights and back-up light glowing...

Time to double check those ground wires and connections


"(same ground that the turn signal bulbs are connected to on the tail light housing)".

That last line would indicate the tail lamp housing isn't grounded. Could check it for a presence of voltage with lights on and then fix or add a good ground wire to the body.

Clay

Oh trust me I did... I can guarantee there is solid ground to those sockets. If I disconnect the grounds from them they actually get brighter but it's because the turn signal filament that is lighting getting more ground through it. Like I said, very strange and why I'm thinking it has something to do with the turn signal assembly.

["QUICK-SILVER"]

Reduced flow/current through the turn signal switch wouldn't make the back-up lamp glow.

Under normal conditions, that would be power flowing backwards through the back-up light bulb hunting ground, from the tail lamp housing not being grounded.

Anything happened under the dash (or anywhere) that back-up light wires are close to turnsignal wires? Got to figure out where the stray volts are coming from and what direction they're headed.

Clay

[torqhead]

Originally Posted by "QUICK-SILVER"

Reduced flow/current through the turn signal switch wouldn't make the back-up lamp glow.

Under normal conditions, that would be power flowing backwards through the back-up light bulb hunting ground, from the tail lamp housing not being grounded.

Anything happened under the dash (or anywhere) that back-up light wires are close to turnsignal wires? Got to figure out where the stray volts are coming from and what direction they're headed.

Clay

Completely agree, as you know from our past this electrical stuff I can deal with but this one has me scratching my head. I triple checked everything. I just happened to notice the reverses light thing which makes it more puzzling but I did the below with all 3 socket bulbs on the left side removed from the light assembly housing, ie: no ground could get to the reverse light socket.

I removed the two 1157 bulbs from their sockets. No need to remove the reverse light bulb for obvious reasons. I did the below on both sockets.

- validated good ground on both left tail lights (2 for the housing on my gto) with an ohm meter. solid dead short

- turn parking lights on, +12 volt positive for proper bulb tip and meter negative lead was on socket ground where bulb would touch, produced proper reading of 12V

-brake or turn signal produced +12V positive on opposing bulb tip connector with meter negative probe on socket ground produced proper reading

Put bulbs back into sockets but did not install in housing. So they are getting exactly what was done above. Turn parking lights on, the proper element lights and they work properly.

Turn the brake lights on, or tune signal and in both cases only the parking light element stays lit or lights.

Maybe another piece that may produce an idea that's a bit baffling is I went as far as to remove the negative leads that go to both sockets. With brake lights applied the "turn signal filament" was not a bright. I could use a jumper between the negative lead of the socket and touch ground intermittently and make it "flash". In a way this tells me I am producing additional ground to the socket.

And before I'm asked , I testing the bulbs directly on the battery and ensured they worked properly and also made sure the proper contact for the proper lead in the socket is correct. I also went as far as using another bulb.

Maybe George will chime in, I know he's our resident electrical specialist. Not that you don't know your chit Clay, just trying to rallying some more brain cells on this one... lol

[76TA462]

Not sure if this long winded idea will help, and its to do with the direct power line to your left sockets. Recently I did some serious gremlin chasing for my front lights (Trans Am). With the light switch pulled out one click to get all marker lights on minus headlights everything worked (lower marker lights and side market lights all bright). When I pulled the switch all the way to put the headlights on, the driver side was all good but the passenger side headlight and lower plus side indicator lights were all dim. I checked and redid all the grounds. Pulled all the wires from the looms and chased them. Same volts on both sides of the car. The driver headlight socket has two leads in from firewall and two out to passenger headlight, plus a power in. The passenger headlight had two leads in from the driver headlight and a power out to the lower indicator light. The sockets were original. Now the bizarre thing – I found a power line from the driver side stranded. Spliced it into the power line going from the passenger headlight socket to the lower indicator light. It was the fix, all good and a very bizarre thing. Without the power line to the passenger headlight there was enough power leaking in the system for all to work until the headlights were engaged. Also from the power leakage, in the dash cluster the passenger side green flasher glowed steady (not as bright as when the flasher was on) when the headlights were engaged, and corrected itself once the power line was spliced in. The power leakage within the otherwise all interconnected system even caused this. Long winded, but maybe there is something in this that might help. Good luck.

[torqhead]

Originally Posted by 76TA462

Not sure if this long winded idea will help, and its to do with the direct power line to your left sockets. Recently I did some serious gremlin chasing for my front lights (Trans Am). With the light switch pulled out one click to get all marker lights on minus headlights everything worked (lower marker lights and side market lights all bright). When I pulled the switch all the way to put the headlights on, the driver side was all good but the passenger side headlight and lower plus side indicator lights were all dim. I checked and redid all the grounds. Pulled all the wires from the looms and chased them. Same volts on both sides of the car. The driver headlight socket has two leads in from firewall and two out to passenger headlight, plus a power in. The passenger headlight had two leads in from the driver headlight and a power out to the lower indicator light. The sockets were original. Now the bizarre thing – I found a power line from the driver side stranded. Spliced it into the power line going from the passenger headlight socket to the lower indicator light. It was the fix, all good and a very bizarre thing. Without the power line to the passenger headlight there was enough power leaking in the system for all to work until the headlights were engaged. Also from the power leakage, in the dash cluster the passenger side green flasher glowed steady (not as bright as when the flasher was on) when the headlights were engaged, and corrected itself once the power line was spliced in. The power leakage within the otherwise all interconnected system even caused this. Long winded, but maybe there is something in this that might help. Good luck.

I can do the rambling on these things, but thanks for sharing this story. It made me go out a verify all other lights on the car work properly. and they do. I also don't know how long this problem has been going on. Could be for a bit as my son noticed it when I had it at the track a month or so ago.