Electrical gurus... Any thoughts on this phantom signal light issue? (not mine)
cdnpont said
Jan 5, 2022
From a ongoing post on ChevyTalk,
On my bone stock 65 2dr HT. For some reason, the bulb stays on (both filaments of the 1157 bulb are lit) when the car is off and the light switch is off. Replaced the bulb and it did function for a little bit (including the blinking bulb). I did have to jiggle the bulb around in the socket for it to work. Then went out to to take out the garbage and noticed that the bulb was magically back on while the car was sitting in the driveway. Electrical gremlins that I can't figure out.
How can both filaments of a 1157 bulb be lit on their own when the lamps and key are both off? It has to be a some kind of short, right?
Just as an exercise, what and how can this be?
beaumontguru said
Jan 5, 2022
Alot of problems can be traced to bad contacts in the turn signal switch. Worth checking
4SPEED427 said
Jan 5, 2022
I would pull the tail light fuse and see if it changes, and if not, reinstall that fuse and pull the brake light fuse. At least that would tell you which filament is getting powered.
If neither one changes it, I'd start pulling fuses to see if you can figure out which circuit is powering the bulb. And once again it won't be a shock if there's a bad ground somewhere and it's finding it's way from an entirely unique circuit that has nothing to do with either of the filaments.
Mike Ward MB said
Jan 5, 2022
I had a similar problem with my 72 Nova. I found that one of the front turn signal pigtail had twisted out of place in the socket. Once I corrected the position of the pigtail and carefully installed the bulb everything worked as it should.
cdnpont said
Jan 5, 2022
Mike. So the lamp was lighting without any apparent switching on?
seventy2plus2 said
Jan 5, 2022
He didn't specify if it's front or rear.
Front: check headlight switch.
Rear: check headlight switch & brake switch.
Something is touching 12 v that shouldn't be.
cdnpont said
Jan 5, 2022
In the title of the post he does state it's the front.
If one front side only is phantom lit, he has to have a short somewhere into the front signal - right or left signal feed wire. A short into the front running light feed anywhere would light both front sides as they're connected together at the engine side bulkhead plug. And the second issue is the socket sounds like it's shorted itself, lighting both filaments of the bulb at the same time.
If it were the headlight switch itself shorting to the running lamp output, he'd have both front running lamps coming on, right? Also, the signal switch has no power going to it unless the key is on ACC feeding the flasher, or the brake lamp switch is closed (which would be lighting the brake lamps).
Also, the running lamps are body grounded on the 65.
Strange, but I find it interesting. I'd love to track it down.
Sometimes on an 1157 when the filament breaks it falls across the other filament resulting in them both lighting up.
I don't think it's been mentioned, has he tried new bulbs?
cdnpont said
Jan 5, 2022
Good point on the loose filament. We've all had this at one time or another.
Yes, as he says, he did install a new bulb and it appeared to function normally. But then the phantom light returned.
Mike Ward MB said
Jan 5, 2022
cdnpont wrote:
Mike. So the lamp was lighting without any apparent switching on?
Indicator in the dash stayed lit, turn signal didnt work on that side, cant remember if the front stayed on but sure had me confused for a while. The pigtail is keyed with a tab on the cardboard to align itself with the socket and bulb. After I put on my glasses I could see that the pigtail had twisted in the socket. With the battery disconnected I fiddled with it to get it realigned, put the bulb in carefully and that fixed the problem.
DANO65 said
Jan 5, 2022
Both filaments lit on an 1157 generally means no ground at the socket and the turn filament is "grounding" through the park lamp filament and over to another park lamp bulb that does have a good ground. As for why the turn is energized when everything is off likely something touching the brake "power" in the turn signal switch.
hawkeye5766 said
Jan 6, 2022
DANO65 wrote:
Both filaments lit on an 1157 generally means no ground at the socket and the turn filament is "grounding" through the park lamp filament and over to another park lamp bulb that does have a good ground. As for why the turn is energized when everything is off likely something touching the brake "power" in the turn signal switch.
Yes..this happens a lot on RV's and campers, the current finds the easiest way back. (that is the both filaments being on....now why is it getting power to turn them on?) Could be a multiple of things like headlight switch,short in wiring, short at firewall bulkhead, fuse panel etc etc. To me the easiest way is to trace the voltage. Like Carl said,pop a fuse until no voltage on meter. Now you know the circuit which is feeding it. Put in fuse and start unplugging what's on that circuit checking voltage every time you unplug something. You will eventually track it down... I once had my dome light turning on my tail light the odd time. What a bugger to find!!! Since the dome light wire is (HOT) all the time and only turns the interior light on when you open the door (grounds the circuit). Both dome light and tail light wiring run under the door sill tapped together and seems the two wires liked each other over the years.... so they touched each other once in a while!
cdnpont said
Jan 6, 2022
Ignition on, he's undone the column plug, and the front right running and dash indicator stay lit. So at least the switch is out of the equation.
I want him to turn the ignition off plug disconnected, to at least see if it's a always hot, or an acc on short into the DK blue FR feed wire.
We know It stays lit ign on, is it a short from the purple flasher feed to that FR feed. If it goes off, then it moves the issue further forward to an always hot cross somewhere.
If it were mine I'd pull fuses as well.
hawkeye5766 said
Jan 6, 2022
65 so column does signal/brake/horn..why leave the ign on when (he says) it's hot when ign off?????? Guy is not helping himself....
On my bone stock 65 2dr HT. For some reason, the bulb stays on (both filaments of the 1157 bulb are lit) when the car is off and the light switch is off.
-- Edited by hawkeye5766 on Thursday 6th of January 2022 01:26:49 AM
From a ongoing post on ChevyTalk,
On my bone stock 65 2dr HT. For some reason, the bulb stays on (both filaments of the 1157 bulb are lit) when the car is off and the light switch is off. Replaced the bulb and it did function for a little bit (including the blinking bulb). I did have to jiggle the bulb around in the socket for it to work. Then went out to to take out the garbage and noticed that the bulb was magically back on while the car was sitting in the driveway. Electrical gremlins that I can't figure out.
How can both filaments of a 1157 bulb be lit on their own when the lamps and key are both off? It has to be a some kind of short, right?
Just as an exercise, what and how can this be?
If neither one changes it, I'd start pulling fuses to see if you can figure out which circuit is powering the bulb. And once again it won't be a shock if there's a bad ground somewhere and it's finding it's way from an entirely unique circuit that has nothing to do with either of the filaments.
I had a similar problem with my 72 Nova. I found that one of the front turn signal pigtail had twisted out of place in the socket. Once I corrected the position of the pigtail and carefully installed the bulb everything worked as it should.
Mike. So the lamp was lighting without any apparent switching on?
Front: check headlight switch.
Rear: check headlight switch & brake switch.
Something is touching 12 v that shouldn't be.
In the title of the post he does state it's the front.
https://www.chevytalk.org/fusionbb/showtopic.php?tid/367351/
If one front side only is phantom lit, he has to have a short somewhere into the front signal - right or left signal feed wire. A short into the front running light feed anywhere would light both front sides as they're connected together at the engine side bulkhead plug. And the second issue is the socket sounds like it's shorted itself, lighting both filaments of the bulb at the same time.
If it were the headlight switch itself shorting to the running lamp output, he'd have both front running lamps coming on, right? Also, the signal switch has no power going to it unless the key is on ACC feeding the flasher, or the brake lamp switch is closed (which would be lighting the brake lamps).
Also, the running lamps are body grounded on the 65.
Strange, but I find it interesting. I'd love to track it down.
I don't think it's been mentioned, has he tried new bulbs?
Good point on the loose filament. We've all had this at one time or another.
Yes, as he says, he did install a new bulb and it appeared to function normally. But then the phantom light returned.
Indicator in the dash stayed lit, turn signal didnt work on that side, cant remember if the front stayed on but sure had me confused for a while. The pigtail is keyed with a tab on the cardboard to align itself with the socket and bulb. After I put on my glasses I could see that the pigtail had twisted in the socket. With the battery disconnected I fiddled with it to get it realigned, put the bulb in carefully and that fixed the problem.
Yes..this happens a lot on RV's and campers, the current finds the easiest way back. (that is the both filaments being on....now why is it getting power to turn them on?) Could be a multiple of things like headlight switch,short in wiring, short at firewall bulkhead, fuse panel etc etc. To me the easiest way is to trace the voltage. Like Carl said,pop a fuse until no voltage on meter. Now you know the circuit which is feeding it. Put in fuse and start unplugging what's on that circuit checking voltage every time you unplug something. You will eventually track it down... I once had my dome light turning on my tail light the odd time. What a bugger to find!!! Since the dome light wire is (HOT) all the time and only turns the interior light on when you open the door (grounds the circuit). Both dome light and tail light wiring run under the door sill tapped together and seems the two wires liked each other over the years.... so they touched each other once in a while!
Ignition on, he's undone the column plug, and the front right running and dash indicator stay lit. So at least the switch is out of the equation.
I want him to turn the ignition off plug disconnected, to at least see if it's a always hot, or an acc on short into the DK blue FR feed wire.
We know It stays lit ign on, is it a short from the purple flasher feed to that FR feed. If it goes off, then it moves the issue further forward to an always hot cross somewhere.
If it were mine I'd pull fuses as well.
65 so column does signal/brake/horn..why leave the ign on when (he says) it's hot when ign off?????? Guy is not helping himself....
On my bone stock 65 2dr HT. For some reason, the bulb stays on (both filaments of the 1157 bulb are lit) when the car is off and the light switch is off.
-- Edited by hawkeye5766 on Thursday 6th of January 2022 01:26:49 AM