Troubleshooting a turn signal indicator

Back when I did the new wiring harness I said that everything was working perfectly. It turns out that was not correct. I did not realize at the time that the new turn signal switch had a light in the handle that is supposed to blink when the signals are on. When I discovered this, I found the light was on dimly when the turn signals are off. The light blinked (dimly) when the turn signals were on. My first thought was a bad ground, so I tested that and it was fine. So today I decided to try and figure out what is going on here.

My second thought was maybe I got a 12V bulb by mistake. So I tested it and it is 6V. Rats, now I am out of easy ideas. Time to look more closely.

I pulled out the flasher to start troubleshooting. This is really simple. “L” is the load (the turn signal lights). X is the switch that supplies power. And P is the “pilot” light which is what my indicator should be tied to.
Just to verify how I thought this worked I took the cover off the switch. Sure enough, that yellow wire runs down the handle from the light and is soldered to the black wire with the white stripe that runs directly to the “P” terminal of the socket. Lets make sure this all works.
First I put a test lead on the “P” terminal using a spade connector to give me something to clip on to.
Then I used a multimeter to check continuity between the light socket on the turn signal switch and the “P” terminal of the flasher socket. Good continuity. So the wiring is good. Hmm… At this point things are looking towards the flasher being bad. So I tried swapping for another one. It did not work either but now the lamp does not turn on dimly at all.
I went rooting though my parts stash and made a test rig. Power is being supplied by my battery charger. The load is an old fog light, the P indicator is an old dash light. The flasher works perfectly but the indicator never lights. So bad flasher? This is the flasher that came with the new wire harness.
This is the flasher that was in the old wiring harness. It is USA made but behaves exactly the same. I even tried putting an analog voltmeter on the “P” terminal, it does not even flicker. Is it possible to have two bad flashers?

In my parts stash I found another, really old and cruddy, 6V flasher. I decided to try it. This flasher has a buzzer in it so it makes a sound when the signal is on. It flashed very quickly but I did see a flicker of light from the indicator. I refuse to accept three bad flashers! The old flasher has screw terminals so I can’t easily try it in the car.

I have never taken a flasher apart to see how they work but I expect some sort of thin bi-metallic strip. When the light comes on the strip heats up and opens the circuit, turning the light off until the strip cools down and closes the circuit again. The car does not have front turn signals right now. I am buying new fog lights to use as front turn signals but those have not arrived yet (a story for another time). Now I am wondering if there is simply not enough load on the flasher so the flasher does not work right. The new “can” shaped flasher might be electronic using a transistor. In which case that could have the same problem. So I am going to wait until all the lights are hooked up and see if that changes anything. If not, I will probably rip apart a flasher and see what is up.


Troubleshooting a turn signal indicator — 2 Comments

  1. Pingback: Front turn signals | 1941 Studebaker Champion

  2. Pingback: New turn signal flasher | 1941 Studebaker Champion

Leave a Reply

Your email address will not be published. Required fields are marked *