Minor electrical problem; possibly a bad ground

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harrisonm

harrisonm

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I've had this minor problem for a while, but it only happens when I drive at night with the lights on, which I rarely do, so I haven't fixed it yet. 69 Barracuda FB. Both front turn signals work fine (nice and bright) when the headlights are off. However, when the headlights are on, there are two things wrong:
1. When I turn on the headlights, without using the turn signal, the right green turn signal light on the dash illuminates, and the right front turn signal/running light will does not come on. If I tap it, it will flicker. Sounds like a bad ground, right? But that light bulb works fine as a turn signal when the headlights are off.
2. With the headlights on, the right front turn signal will blink, but it is not nearly as bright as when the headlights are off.
Rear turn signals work fine. I was thinking that I might have a ground problem. But if that was the case, why would the right front turn signal work fine with the headlights off? But when the headlights are on, and the right front turn signal/running light does not come on, but it will flicker when I tap it makes me think about a bad ground. So somehow the headlights being on is causing my problem. This is really irritating, since I am usually pretty good with electrical problems. Not as good as @67Dart273, of course, but pretty good.
 
Sounds like might be ground to me Do you have your car wired so the park lights stay on with headlights?
 
If there's one thing I've learned about electrical in old cars in the past few weeks, is to clean, the damn, grounds, even if there seems to be power going through. My taillights and interior lights were half working, until I cleaned every connection I could find associated with lights, and bam. Lights working 99.9% of the time. (One of my tail light sockets is janky.)
 
67Dart273 said:
Sounds like might be ground to me Do you have your car wired so the park lights stay on with headlights?
Click to expand...

His car should be wired like that from the factory. The first year that was required was 1968.
 
Any time a turn indicator comes on with the park lamps the fault is lack of ground at that front fixture. Look for chassis ground wires attached to the radiator support. Rear fixtures cannot produce this problem because... This back feed path is interrupted by the turn signal switch.
 
RustyRatRod said:
His car should be wired like that from the factory. The first year that was required was 1968.
Click to expand...
Brain fart

OP here is how this works. "Let's say" you have the left front ungrounded. The parking or headlights are on, no turn signals. Because the fixture is ungrounded, the powered parking lamp filament has no direct ground, and power flows on through the TURN filament and that wire is connected to your turn indicator(s) which is/ are grounded, so that power lights up the indicator

When the turn signal is activated, the turn filament becomes powered of course during "flash" so at that point both filaments are powered with no ground, so the turn lamp won't light, but power is going to the indicator, which likely "lights brighter" during the flash.

Another great example was the popular Chevs about 60'ish to ?? 66?? which had "some" of the lighting in the TRUNK LID. Just think about THAT for a minute.........If the trunk lid had no good solid grounding jumpers from the lid to the body........and the wiring had problems.........and it often did........you used to have "interesting" effects........With the tail lights on, the lid mounted light would be dim and the body mounted lamp would be normal. when you activated the signal, the trunk mounted lamp would go out as the other one flashed turn.

The lid mounted light would get tail power.......no ground........through the tail filament........through the turn filament.......;and "maybe" to ground through the turn filament on the other side, through the brake light circuit in the turn signal switch.
 
67Dart273 said:
Brain fart

OP here is how this works. "Let's say" you have the left front ungrounded. The parking or headlights are on, no turn signals. Because the fixture is ungrounded, the powered parking lamp filament has no direct ground, and power flows on through the TURN filament and that wire is connected to your turn indicator(s) which is/ are grounded, so that power lights up the indicator

When the turn signal is activated, the turn filament becomes powered of course during "flash" so at that point both filaments are powered with no ground, so the turn lamp won't light, but power is going to the indicator, which likely "lights brighter" during the flash.

Another great example was the popular Chevs about 60'ish to ?? 66?? which had "some" of the lighting in the TRUNK LID. Just think about THAT for a minute.........If the trunk lid had no good solid grounding jumpers from the lid to the body........and the wiring had problems.........and it often did........you used to have "interesting" effects........With the tail lights on, the lid mounted light would be dim and the body mounted lamp would be normal. when you activated the signal, the trunk mounted lamp would go out as the other one flashed turn.

The lid mounted light would get tail power.......no ground........through the tail filament........through the turn filament.......;and "maybe" to ground through the turn filament on the other side, through the brake light circuit in the turn signal switch.
Click to expand...
Get this... In the 80s a lot of GM vehicles had side markers that were on with park lamps and would flash with turn. How did they do that with a single filament #194 bulb?... The front fixture wasn't grounded at the fixture. The ground path was through that side marker bulb. So when a turn indicator in the dash came on with park lamps, you had a burned out side marker bulb.
 
All fixed. Thanks for the inputs. It was a ground. The turn signal housing was not grounding. So I ran a short wire from the light harness ground screw near the right horn to one of the studs that attaches the housing to the bracket. Works fine now. I kept thinking it might be a ground, but if the ground was bad, why would it work in turn signal mode with headlights off?? Oh well, it's fixed. Special thanks to
@RedFish, @67Dart273, @Tylan and @Murray.
 
harrisonm said:
All fixed. Thanks for the inputs. It was a ground. The turn signal housing was not grounding. So I ran a short wire from the light harness ground screw near the right horn to one of the studs that attaches the housing to the bracket. Works fine now. I kept thinking it might be a ground, but if the ground was bad, why would it work in turn signal mode with headlights off?? Oh well, it's fixed. Special thanks to
@RedFish, @67Dart273, @Tylan and @Murray.
Click to expand...
Current seeks ground, even jumps to ground. The ground it found was at the inst' panel. thats why turn worked. Park circuit found same ground via backfeed through turn. Hope that splains it.
 
RedFish said:
Get this... In the 80s a lot of GM vehicles had side markers that were on with park lamps and would flash with turn. How did they do that with a single filament #194 bulb?... The front fixture wasn't grounded at the fixture. The ground path was through that side marker bulb. So when a turn indicator in the dash came on with park lamps, you had a burned out side marker bulb.
Click to expand...

Yup. Knew about that.
 
RedFish said:
Current seeks ground, even jumps to ground. The ground it found was at the inst' panel. thats why turn worked. Park circuit found same ground via backfeed through turn. Hope that splains it.
Click to expand...
Great explanation; THANKS. I am pretty good with automotive electrical, but that stumped me.
 
67Dart273 said:
Brain fart

OP here is how this works. "Let's say" you have the left front ungrounded. The parking or headlights are on, no turn signals. Because the fixture is ungrounded, the powered parking lamp filament has no direct ground, and power flows on through the TURN filament and that wire is connected to your turn indicator(s) which is/ are grounded, so that power lights up the indicator

When the turn signal is activated, the turn filament becomes powered of course during "flash" so at that point both filaments are powered with no ground, so the turn lamp won't light, but power is going to the indicator, which likely "lights brighter" during the flash.

Another great example was the popular Chevs about 60'ish to ?? 66?? which had "some" of the lighting in the TRUNK LID. Just think about THAT for a minute.........If the trunk lid had no good solid grounding jumpers from the lid to the body........and the wiring had problems.........and it often did........you used to have "interesting" effects........With the tail lights on, the lid mounted light would be dim and the body mounted lamp would be normal. when you activated the signal, the trunk mounted lamp would go out as the other one flashed turn.

The lid mounted light would get tail power.......no ground........through the tail filament........through the turn filament.......;and "maybe" to ground through the turn filament on the other side, through the brake light circuit in the turn signal switch.
Click to expand...


I just had the same thing happen to me after working on the car for the last 4 months. Just took it out and the indicators in the dash turn on ( and you'll love this) with the parking lights and the fuel and temp gauge won't work when the lights are on. I think I need to reground the cluster.
 
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