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Just replaced just about every bulb under the dash and exterior. Worked great until randomly the right turn signal arrow indicator turns on with the lights.
It did this a few weeks ago but I believe on the left, then stopped, now on the right. Indicator and outside bulbs stay on, no flashing unless the indicator is turned on.
kinda weird and want to see if there’s a way to fix it.
Mine did exactly that just a couple weeks ago. Right indicator on the dash was lit with the lights on. I don't go out in the dark often but that evening I was test driving the car. And did that ever bug me! On mine it was the ground at the socket. Put in a new bulb. Fixed up the ground wire on the socket, all was normal again. 5 minutes.
Had a similar problem on my 75. Mine was the left hand TS indicator would glow when I turned the headlights on but the TS would work properly when activated.
I found when I removed the front left TS bulb in the grill the problem would go away. Seems the headlight current was finding a better ground by back feeding through the left TS circuit. Oddly enough with the TS bulb removed the headlights would still work.... Very strange...
I disconnected & cleaned two grounds, one located on the upper metal crossover frame near the horns and the other down on the lower front crossover frame near the radiator. Don't know which one corrected it but haven't had the problem since (well over a year).
Like a previous poster said, always check the grounds.
Good luck
This feedback to other circuit’s phenomenon happens only with two filament bulbs like the 1157 or circuits where single filament bulbs share the same ground wire. The diagram below is simplified to illustrate a schematic of a typical two filament bulb. In the case where an 1157 is working properly (Diagram A) you can see when voltage is applied to the park circuit (indicated by the green wire) it goes through the element and straight to ground. The ground being the shortest path, the filament glows like it should. The same is true with the directional circuit, power would just flow up the other side indicated by the blue wire and then to ground.
In diagram B where the ground is weak or faulty the shortest path no longer exists however the voltage has a second path and that is through the other filament. So in this example, where power would normally be applied TO the lamp by the blue wire, the power is now applied to the blue wire FROM the bulb itself and that power will find its way back to your instrument cluster. I know... my 1157's look like they were drawn by a 9 yr old on Windows 95 but you get the point.
LED’s make this even more interesting, that for another time.
There are ways to make LEDs less interesting. Downright boring, in fact. To the point that they simply work like ordinary bulbs, while emitting more photons, and using a tiny fraction of the current.
I found a ground wire connector broken inside on of my taillight sockets, which gave me similar issues to what @ZIOGEO describes. Replacing all of the sockets was a cheap and easy fix.
Turn signal indicator on
