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Have a ’50 Chevy AD ½ ton. When I turn the left turn signal on, all turn signal lights, both sides flash. The right turn signal works fine. What could cause this? Nothing has been changed.

Frank,

Because everyone else mentions this when electrical problems pop up, I guess I will too...check your grounds! I don't really know what this means, but I don't want to be left out.

I would try a new flasher unit, and would also replace the left hand turn signal lamp.

Do both brake lights work OK when you just mash the brakes?

Stuart

Ground. Ground. Ground. Do a search and you will find a description of why your lights are doing that.

Do all the lamps glow at full intensity when the left turn signal is on?

Cletis,

I'm not clear on this ground thing. If the left brake light were the culprit, what path would the power take to illuminate the other side in its quest for ground.

How about a 'worst case scenario'. :confused:

Stuart

There could be a problem in the turn signal switch itself, but if it is ground problem on the left light assembly, the lights shouldn't glow with full intensity. The path would be from the left turn light, either front or rear, through the light filament to the tail or parking lamp, through one of those filaments to the tail light wires and back through to the lights on the other side to get to ground. But, I repeat, none of the light should have full intensity in this scenario.

Baldy,

I followed the path you described, but am still confused how it can go through the opposite side light to find ground. If a left turn is indicated, wouldn't the circuit on the right lamp, in a backwards direction, be from ground, through the filament, down the wire to a open contact in the turn signal switch.

If the left lamp can't find ground through its housing, how can it find ground through the adjacent lamp.

It isn't that I don't believe this, it's just that every time a electro-gremlin pops up, the entire peanut gallery shouts 'grounds'...

If I could understand how that potential was traveling back to the battery, and lighting various lamps as it made this trip, I could rest my pea brain.

These are general comments, not pointed at a particular member.

Stuart

It's going through the tail light wire or the parking brake wire, not the brake light or turn light wire to get to ground. That is why panel lights come on in this scenario if the panel lights are not isolated from the taillight circuit. As an experiment, remove you taillight assembly from your fender, and if it doesn't have a ground wire to it, turn on the turn indicator in the dark and you will see what other lights come on.

I 'think' I understand...thanks!


Stuart

It is possible to travel back through the tail light circuit because of the way the bulb is built. There at two filiments attached to one post inside the bulb. That post should be grounded. If it is not, power from the turn circuit travels across the tail light filament, activating all other lights on that circuit until it finds a place where it can ground. And yes, they will be dimmer than normal.

sounds to me like the wires are switched. Instead of actuating the left turn signal you are actuating the parking lights and the rear running lights via the flasher. This is the only way both front and both back can flash off the turnsignal that I can see( check to see which filiment is actually lighting). I'm not a eletrical guru but if all lights are flashing then there is a common wire to them all and in this case it doesn't really sound like a bad ground to me. Sounds like a direct wiring issue.

Did you happen to read the post directly above yours? The common wire is the one in the bulb that both filaments are attached to.

cjoe,

I think you must remember, that anything that conducts electricity could be thought of as a wire. Technically, the entire frame of your truck is a big wire.

When power goes into a lamp, and can't find the conventional ground, it will head back through the other filament, down the wire, into the lamp on the other side, and out through the lamp base to ground.

As it does this, that opposite light will illuminate, slightly, as current passes through it , using its properly grounded base to return to zero potential.

I think this is how it works. I was enlightened by Baldy and Cletis just last week, so I might have it wrong. If you draw a little cartoon of the lights and wires, you can trace a path that makes it more clear how this bizarre action could take place.

Stuart

my mistake Cletis, I read your post and missed the idea that the common was the ground (or actually, in this case..the missing ground). I now understand that if the ground was ok the lights would flash normally but without the ground the current continues on thru the second filament in search of a ground further on. This scenario would continue until a ground is found. All affected lights will be lit but dimmer than normal (because of the increased wattage on the circut???) It is a concept that is a little difficult to understand but as Stuart suggested, a hand drawn picture makes it easy to see.
Thanks Cletis and Stuart for explaining this strange circut, I may need this info myself one day.

It was a bad ground on the left front turn signal. Too dirty that it wasn't grounding.