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Help with LED turn signals on ‘38


rodneybeauchamp

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So, I thought all my problems were solved with my turn signal lamps on my ‘38 by using LED park/turn signal globes up front and standard globes at the rear in a seperate lamp. (Not though the brake lamps ) These are 6volt double contact LEDs and work fine when tested on the battery.

 

What happens when they switch on either left or right is that both front turn signals flash along with the rear of that side.

 

It seems that the power is feeding back via the common earth and powering the other globe. My test light shows this too!

 

Currently the only way I can get it to work as it should is when I disconnect the park light side of the wiring on one or both lamps.

 

When fitted with standard incandescent bulbs they work fine except they generate too much heat for my liking. Flash rate is fine with a 6V Tridon Electronic flasher ( not an LED type) with either bulb combination.

 

I have yet to wire up the headlamp switch as yet, hoping that I could get these turn signals tested first.

 

Any thoughts how I can get this working as it should?

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It seems peculiar that both fronts flash while only one one rear does.  Left and right should be separate circuits.  If I had to guess, I'd say that what's happening is that the LEDs are creating a circuit between the turn signals and the parking lamps.  When you energize the signal, it also energizes both parking lamps.  Check the contacts on your LEDs.  Make sure that the layout, dimensions, etc. are identical to those on the bulbs.  And try this: check for continuity between the two terminals on the LED.  Or put 6V on one terminal and test for 6V on the other.  You might just have some crappy LEDs.

 

Think about this..  A standard dual-use bulb (e.g. an 1157) has two filaments and two separate circuits.  This LED likely has one array of diodes that can be energized from either of two terminals.  If designed properly, there would be a diode on each terminal to prevent current from flowing back out the other terminal.  Absent those diodes, you've got a direct short between the two terminals.  Try disconnecting the turn signal wire from one side and checking if both lights still flash when you use the other signal.

Edited by KongaMan (see edit history)
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Thanks Kongaman,

i have been able to get it to function properly on the flasher side by doing any  the following, 

-removing the other side globe

-cutting the wire that feeds the park light on both sides

-removing the earth on the opposite side

 

what seems strange is that when the flasher is on the park light circuit on that side has power enough to light my test light.

 

Put it all back together with incandescent globes and it works as it should. Perhaps the LEDs I bought don’t have a diode feature to prevent back feed. 

 

Anyway see see what answers we get on the forum.

cheers

Rodney 😀😀😀😀

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On ‎1‎/‎28‎/‎2019 at 2:43 AM, rodneybeauchamp said:

what seems strange is that when the flasher is on the park light circuit on that side has power enough to light my test light.

 

That doesn't seem strange at all if the LEDs are made incorrectly, as they would provide a dead short between the flasher circuit and the parking circuit.

 

Disconnect the parking light on one side, then turn on that flasher.  Does the other parking light still come on?

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Hi, I will try that. At the moment I am rechecking my globe sockets to make sure there are no stray wires that could create a circuit. I have just redone the RH one and checked for continuity and resistance.

 

What I did test was that the LED lights up correctly on the park and turn circuits in the globe holder while it was out of the vehicle  circuit. Will check again when installed. I have also removed all globes from the front and rear turn lamps as well as the stop and tail lamps. When wired back in I will test one by one to see if there is a stray feed anywhere.

 

thanks for your help, will keep you posted. 😀😀😀😀

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Kongaman

 

Your right, I was doing a lot of unnecessary work. You may wish to check my response in the technical forum where I tested them in a made up circuit out side the car. Same result!

 

Im half tempted to put two diodes in the circuit at the park light power wire, thinking that this will allow current to flow one way in to the bulb but not back out of it. Have also contacted the supplier/ manufacturer and see what they come up with. Their bulbs are specified for brake, turn signal and park, so they should work same as incandescent bulbs.

 

Again will keep you posted, cheers

 

Rodney 😀😀😀😀😀😀😀

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If I understand this correctly from reading your other thread, the situation is that each LED has two diode arrays.  When voltage is applied to the parking terminal, one array lights.  When voltage is applied to the signal terminal, both arrays light.  Which means that every time a turn signal flashes, both the left and right LEDs will blink, because the voltage which drives the common array also feeds the parking circuit which is connected to the other side.

 

See this professionally drawn schematic:

 

Buick-LED.jpg.2ad3c2a5015bdd6da7ea630ee6d43b6b.jpg

 

If that's right, these are junk.  Replace them.

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I couldn’t have drawn it so good. Yes, you are spot on, because the park side of the leds are joined, both will flash.im just waiting on a reply from the supplier, and refund too I hope. I will then go back to SuperBright LEDs as I have had good success with my Riviera replacements. I couldn’t find the 6V ones until Matt gave me the information. Otherwise I would have ordered from them 

 

Rodney 😢😢😢😢😢😢

 

 

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As an aside,

are the original ‘38 Buick parking lamp lenses glass or a type of plastic?

 

If originals are glass, does anyone have a pair for sale? Driver quality is all that is required? Don’t mind buying the complete lamp if necessary.

 

Thanks

Rodney 😀😀😀😀😀😀

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Yes they were originally glass. There have been several different individuals over the years that reproduced them in plastic before the glass reproductions were available.

 

Bob's typically has them, but I see that they are currently out of stock:

 

https://bobsautomobilia.com/fender-lamps-pads-and-items/parking-light-lens-1937-38-.-pl-378/

 

Cars, Inc. looks like they have them:

 

http://www.oldbuickparts.com/product_info.php?cPath=35_39_78&products_id=287

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Well, problem solved. Turn signals working as they should, one side at a time. Park lights working too, independent of turn signal.

 

Many thanks to all and sundry for help and advice.

 

And with the parcel arriving today with a replacement ammeter, oil and gas caps and wiring clips it felt like Christmas 😀😀

 

happy Rodney 😀😀😀😀😀😀😀😀😀😀😀😀😀😀😀😀😀

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  • 2 months later...

Well, another update!

 

After I got her back on the road running again, turn signals started to play up. I had already invested what seemed half a lifetime troubleshooting the LEDs, so I went back to the good old incandescent 6volt globes.

 

This gave great results, bright and easy to see and a reasonable flash rate. My only issue that I need to monitor is the heat generated by the bulbs. My light lenses appear to be made of a plastic material, not glass, so will see how they fair.

 

BTW this series 40 did not have the front side lights remain lit when the headlights were turned on, so I moved the wire on the switch one place forward. And now they stay on with the headlights, look so much nicer at night.

 

Our switches for the RHD version are much simpler and don’t have the 4 positions stated in the shop manual. Possibly GM-H used a Pontiac or Chevrolet switch for cost saving and standardisation down under!

 

Took her out for her first run at night since upgrading the head lights lights with 6V relays. Nice and bright, but my aiming is way way off as all I can see is the koala bears in the gum trees. But we are getting there, next step is to install the heater I got some time back, and some seat belts!

 

Photos from a recent local coffee n cars we have in our town, with a run out to a speed boat Aquafest event on the river. Fast and loud!

Rodney 😀😀😀😀😀😀😀

062D484F-7DBF-42BC-A775-93BC2A994D12.jpeg

D0201CF4-70BF-4E61-BD8B-76F8EECE51AC.jpeg

013FACD4-3DC6-4CAD-A299-2C3A854A5932.jpeg

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