Interesting electrical puzzle

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Tom Wells
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Interesting electrical puzzle

Post by Tom Wells » Wed Sep 05, 2018 8:08 am

I have encountered an interesting electrical puzzle. I have arrived at a compromise, but am still curious about why it happens and whether there's anything practical I can do to eliminate it.

The Cobra has six lights for brakes and parking. Two parking lights in the front, and four separate taillights.

All six bulbs are 1157 dual contact/dual filament bulbs.

I'd like to change all the bulbs to LEDs.

So far, if I put LEDs in the four taillights, everything works as it used to: all the stop/turn/parking lights work normally. It works fine with the original flasher.

If I put LEDs in the parking lights, everything works except the turn signals. The turn signals just never flash.

I have read that the old-style flasher just makes them flash rapidly, but that doesn't happen. There is no flashing at all.

So I got a flasher supposedly made just for LEDs and tried it - same result - no flashing at all.

I have reverted to the incandescent (two) front and LED (four) rear bulbs and the original flasher, and all works fine.

Question: is there a way to get the parking lamps converted without too much fuss, or should I just leave well enough alone?

Tom

mooreken
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Joined: Sat May 09, 2015 12:25 pm

Re: Interesting electrical puzzle

Post by mooreken » Wed Sep 05, 2018 1:20 pm

I have tried LED's 3 times all three caused trouble. Some right away and others after a while. I think it comes down that theLED's don't have the resistance that the filaments do. So the currant goes hunting for another way to get what it wants.
When LED's first came out you had to use a ballast resistors to make it work.

I had LED's in the rear on mine and they worked for quite a while then everything went crazy. I took the dash apart hunting for a broken ground sense the dash lamps were coming on when I hit the brakes. And I had taken the dash out working on my Temp gauge. I finally just did the bulbs as a hail mary and it fixed everything.

So I would try just using 1157's in everything and see if all is well and then put in the LED's one at a time to see if one is defective. But for my car I'm sticking to bulbs.

Ken

BlackSnake
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Joined: Mon Jul 13, 2015 4:09 am

Re: Interesting electrical puzzle

Post by BlackSnake » Wed Sep 05, 2018 2:48 pm

Tom,

Reminds me of the time I installed platinum plugs in my car with MSD ignition...you remember how well that turned out...:roll:

Tom Wells
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Joined: Fri May 08, 2015 7:34 pm
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Re: Interesting electrical puzzle

Post by Tom Wells » Wed Sep 05, 2018 3:40 pm

Ken,

Thanks for the ideas. Tried six different LEDs. Same result. Now have bulbs in front, LEDs in rear; seems to work OK so it'll stay that way until it becomes a problem (again!)

Mike,

I remember! It almost shortened Rick's life a couple of years...

Maybe this weekend for the windshield?

Tom

BlackSnake
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Re: Interesting electrical puzzle

Post by BlackSnake » Wed Sep 05, 2018 9:06 pm

Sure, I'll be there.

Tom Wells
Posts: 394
Joined: Fri May 08, 2015 7:34 pm
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Re: Interesting electrical puzzle

Post by Tom Wells » Mon Sep 17, 2018 12:24 pm

Update today: basically back where I started, but a little more puzzled.

The current setup (not a pun...) is 4 LEDs in the rear, two incandescents in the parking lights up front, and the original 12V flasher.

I put up a note on the ClubCobra site and got some interesting information from a guy who signs on as Unique427 who told me that the reason the LED flasher doesn't flash is because the wiring is probably polarity-reversed at the flasher.

He further said that the original incandescent-type flasher will work OK with reversed polarity, but the solid state one won't.

So I checked, and sure enough the polarity was backwards! I optimistically reversed the leads (a 5 minute job that took nearly an hour-don't ask...) and plugged in the LED flasher. It flashed! At least it flashed the indicator light on the dashboard - but not the exterior lights which remained steadfastly off.

The original thermal flasher went back in and everything works as before. I did prove the thermal flasher was immune to polarity, but no joy with the solid state flasher.

Perhaps if I put in all LEDs and tried it again? I'm not holding my breath. If it works I'll add a note here - if not, not. Sigh.

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