Mysterious LED turn signal problem

T

Thearne3

Member
Hi all,

I have a stock 6v positive ground electrical system in a ‘29 Phaeton. I had been using ‘900’ style lever mechanism (like what Snyder’s used to sell). Only the turn signals are 12v (isolated using an inverter and separate ground wires). The lights are a set of LEDs (orange - mounted in the bumpers). This worked well with a 12v LED flasher relay.

I have always preferred to use original light fixtures, if possible. I recently installed cowl lights and decided now was the time to ditch the 12v turn signals and use the cowls and tail brake lights for turn signals on the original 6v system. No more extra wires and lights!

Set everything up with the same 900 lever and a 6v LED flasher relay. All my lights are LED. Everything checked fine, blinked correctly, worked with the brake, etc. I decided to go for a quick test drive. However, with the engine running (any rpm), the blinker became very erratic. Other than a slightly higher voltage, I can’t think of what could be different engine on vs engine off - a mystery!:confused:

Any ideas? I may insert a voltage regulator in the lead to the relay - maybe that will clear up the issue…
 
Electrical Noise is likely interfering with the electronic 6v flasher relay. You might be able to "filter" some of the noise with a capacitor, or another brand flasher may work better.
 
The non-resistor plugs in these cars throw off a lot of RF static. I would call one of the vendors and ask for their 6V+ electronic flasher; they'll be sure to stock one that's resilient to interference.
 
I agree with previous posts about RF noise interfering with the turn signal circuits.

You might try installing a ferrite core RF choke on the power line to the turn signal controller - and maybe also on some of the long wires running to the LEDs from the controller. You can get these RF chokes on Amazon, in clip-on and other styles. You may need to experiment a bit.

Good luck !
Jim
 
What's the current rating of the relay? Your bulbs will draw more current when the voltage rises, so maybe it only works with the engine off because the relay can only JUST handle the current of the bulbs?
-> Check if the combined current of your bulbs exceeds the rating for the relay.
 
Yep, I believe the fellas are correct. You're probably getting a lot of 'noise' from the generator and ignition system.

Another/different electronic flasher may work. Thermal flashers don't worry about 'noise', but you'll need more load to use one.
 
What i have found with LED bulbs is every fixture (headlight, cowl light, taillight..) MUST have a dedicated ground wire to it. I've installed Led's on several cars and one worked fine for a while and then went crazy. We ran independent direct grounds to each fixture and the problem was resolved.
 
Thanks for all your inputs! I guess I was lucky to have independent ground to each light in my first set up. I’ll report back as I try each option.
 
Hi all,

Tried the ferrite filters - no joy.

Put in an inexpensive ($13?) buck converter and ‘presto’, success so far. Will report if this result changes, but it would appear that this is working…

Best,
Tom
 
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