New LED front turn lights not working right...

[EricS]

When installing LED bulbs for the turn/brake light signal system, you must use electronic flashers, and the front side marker lights need to be
"non-polarity" sensitive. The front parking light switches the ground on the side marker light during the flashing process, so if it is polarity
sensitive, it will not work. If you look at specs of the bulbs they will generally specify this, but if they don't, assume that they are polarity
sensitive. I never would have guessed these bulbs even existed, knowing LEDs are typically polarity sensitive! Mine all work correctly now after
learning and doing this.

 

[RF_Burns]

Eric,
Non-polarized LED's have either a built in bridge rectifier or two sets of LED's wired with the polarities opposite each other.

It was a neat trick how GM wired the front side lights that way on their vehicles.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

 

[john r. lebetski]

Bruce that one gets ‘em every time. The GM engineer design parameters were not for LEDs at some future date. Right up there with the designed high
blower over voltage trick by design. Me, I’m fine with incandescent lamps in classic vehicles and love the warm look.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Jim Hupy]

I got an education on polarity when I converted my GMC 78 Royale's
clearance lights on the roof. I bought all new led lights and hooked one of
them up and turned the power on, and nada, nuttin', and scratched my head
and exclaimed Wth!. So, out comes my trusty Fluke 77 and it told me the
story. No rhyme or reason to the wiring. Polarity on all of them was
different. So, turn on the power, check the polarity, hook up the led,
repeat x 10. Same is true throughout the whole 12 volt system in the coach.
Incandescent's don't care about polarity. Led's definitely do. Now I check
first, then proceed.
Jim Hupy
Salem, Oregon

On Sat, Apr 2, 2022, 12:21 PM John R. Lebetski
wrote:

> Bruce that one gets ‘em every time. The GM engineer design parameters
> were not for LEDs at some future date. Right up there with the designed high
> blower over voltage trick by design. Me, I’m fine with incandescent lamps
> in classic vehicles and love the warm look.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[Matt Colie]

> I got an education on polarity when I converted my GMC 78 Royale's clearance lights on the roof. I bought all new led lights and hooked one of
> them up and turned the power on, and nada, nuttin', and scratched my head and exclaimed Wth!. So, out comes my trusty Fluke 77 and it told me the
> story. No rhyme or reason to the wiring. Polarity on all of them was different. So, turn on the power, check the polarity, hook up the led, repeat x
> 10. Same is true throughout the whole 12 volt system in the coach.
> Incandescent's don't care about polarity. Led's definitely do. Now I check first, then proceed.
> Jim Hupy
> Salem, Oregon

Fortunately, when I mounted the first of the LED clearance lights, I turned it on because I was curious what it would like like. It didn't. Also
fortunate was that was one of the few where I could get to the connectors. So I reversed the polarity and it looked good. I mounted the other nine
powered up.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit