Magneto interference with LED turn signals

[Dave Young]

I’ve got a stand-alone 12 volt system on my T to power tail lights, front markers and rear turn signals. It functions fine with the engine off but will not flash the turn signals when the engine is running. The system has worked perfectly for 5 years with a magneto-less engine in the car. Now, with a different engine and a very healthy mag, problems.

I’m running an E-Timer still, as with the old engine, and the mag energy goes unused. The 12 volt system has totally independent grounds and has no connection to the chassis. The starting/headlight system is 6 volt.

I’m suspecting some sort of electrical/magnetic interference messing with the electronic flasher unit that is necessary with the low-draw LED lights. Has anyone else experienced this and resolved it? The flasher is under the front seat, about 36” from the magneto.

I’m considering putting a regular timer back on the car, running it on mag and see if it changes. Any ideas would be appreciated.

[Dave Young]

Also, I’ve got the same lighting arrangement on my touring, running an I-Timer on mag, and never had any problems.

[Art M]

I would try grounding the magneto post. Don't know if it solves anything, but it is easy to do.

Art Mirtes

[Ed Fuller]

Hey Dave!

Try switching a couple of the LED bulbs for good old fashioned incandescent bulbs and see how it acts.

When I was putting my speedster together, I had some strange issues with my LED turn signals. Swapped a couple for incandescent and they acted normally. My only guess was the flasher needed more of a load even though it said a load wasn’t needed.

Ed

[TXGOAT2]

The generator is capable of causing interference. You might try disconnecting and grounding the generator and see if that helps. The magneto has no brushes and is a low voltage, low frequency device. I would not want to ground it. It has permanent armature magnets, and grounding it might cause it to overheat or demagnetize it. Wiring to turn signals might pick up interference from the generator and/or the ignition system.

My 1927 open car has LED turn signals connected to the stock 6 volt system with a functioning magneto, which I use regularly. I've had no issues whatsoever with the turn signals. It has LED signal lights and a little plastic "magic box" with the control buttons that is attached to the dash to the left of the steering column by a magnet. Headlight and tail lights are regular incandescent.

The generator uses a standard cutout.

I have a Garmin device attached to the windshield that is connected to its own small 12 volt battery located under the seat. I've had no issues with it.

[Dave Young]

Thanks guys. I’ll tie two 1157’s into the signal terminal block and see what that does and then disconnect/ground out the generator. Grounding the mag post kinda irks me, knowing how difficult it can be to fix if I damage it.

[jsaylor]

I tried LED turn signals. No mag. just distributor. Worked fine when engine was off. With the engine running I tried the turn signal and no flash. The solid state flasher shorted. Thinking I had a bad flasher, I tried another one. Same thing. I discovered there is 20 volts AC on the DC battery circuit. Not sure if its the Dizzy or generator. The generator is an early 60's two brush with regulator I have just received a generator noise filter but haven't had time to install yet. If this doesn't work then I'll add load resistors and a mechanical flasher.

[Norman Kling]

You have a 6 volt starter system but a 12 volt lighting system? What are you using to charge the 12 volt battery? Is If it is connected to the magneto, that could be the problem. Have you tried grounding the negative side of the 12 volt system to the chassis? What year car do you have? Is the 12 volt battery completely surrounded by grounded steel, such as it would be in a 26-27? Or is it open underneath of setting on a wood surface? Somehow you are getting induced current from the magneto into the lighting circuit. You might need to use shielded wiring for the lights and ground the shield of the lighting wires.

Oh! it is so much simpler to leave the T as Henry made it
Norm

[Dave Young]

Norman. The 12 volt is a little battery in a box that’s made for trailer break-away service. With the LED bulbs, it powers them for about 3 months of weekend use, then I just plug a 110 battery charger to it and bring it right back up. It’s a worthwhile addition here on the east coast given the traffic we have to contend with and I do drive a fair bit at night. Like I said up above, the whole thing works fine on my 26 Touring, too. This bitchy one is on my 26 RPU, both surrounded by metal. The generator may be my issue and I’ll see what happens along that line. I definitely agree that Henry did it best!

[Steve Jelf]

I'm using 12 volt LED signals and tail/brake lights on my 1915. The battery is charged by the magneto using the John Regan design. I don't find any interference from the coils or mag. I think your problem may be the type of flasher you're using.
https://www.youtube.com/watch?v=lH85w4Yqhi4

[TXGOAT2]

I don't think your magneto could induce any significant AC power into your DC system. If you can get a 20 VAC reading on the DC side of your T system, there must be a switch issue or a wiring short between the two systems.

I have a Garmin device and an LED turn signal outfit in an open car that runs well on either battery or magneto. It has an Optima 6 volt battery under the seat cushion. The turn signal wiring is fully exposed to the other wiring alongside the engine and under the dash. The LED turn signal system runs off the stock 6 volt T system with a stock generator and cutout. All lighting except the turn signals is regular incandescent. The Garmin navigation device is powered by a small 12 volt battery under the seat. No shielded cable is used. Ignition is 26-27 stock Ford. The car runs on magneto most of the time.

[Norman Kling]

That's a big puzzle. I know this about the magneto and coils in a T. It can jam an AM radio. One time I had my T running in the garage and I got in my other car with the AM radio turned on. It made a lot of static and continued until I got about 200' from the house. Anyway, something is incompatible with your lights and ignition system. I have not used the e-timer. I wonder if that could have any affect on the problem?
Someone else might have the answer. The only way I could find it if it were on my car, would be to experiment with one part at a time until I found which one is causing the interference.
Was there anything other than the magneto which you changed between the lights worked and when the trouble started? Those are the first things I would try first to see what caused the trouble.
Norm

[Dave Young]

This whole engine is from another vehicle, including the generator. I rebuilt this mag when I did the engine and it puts out really good. I’m gonna stick a generator on there without a drive gear on it and see what happens. The flasher could have gone goofy too, I suppose. Steve, what flasher are you running? I’ve got this same flasher on 3 other cars. I’ve opened up the old 6v mechanical flashers and bent the bi-metal contacts to open with less load and still give a decent flash rate, but these electronic ones were easier. Nice video Steve.

[Dave Young]

Pat, your last sentence…. The car runs on magneto most of the time. That’s the one that I’m wondering about with my setup. My mag isn’t being used due to my having an E-Timer on this one.

[TXGOAT2]

I have a New Day type timer.

Note that grounding the T generator will stop it from operating.

Grounding the T magneto will NOT stop it from operating, since it has a permanent magnet rotor. The magneto would continue to draw power from the engine and would probably overheat.

I don't think the magneto is the source of either radio interference or any interference with modern electronic devices not directly connected to it.

My 27 car does not emit significant radioo interference. FWIW, An old portable AM/FM/SW radio works well in or near the car with the engine running. Stronger AM stations easily overcome the background interference from the ignition system and generator. Fringe area FM is totally unaffected.

I'm pretty sure the magneto emits no significant interference that would affect modern electronics not directly connected to it. The stock ignition and generator very well might, but on my car, they do not.

Concerning the ignition system:

The earlier cars with a wooden coil box and long high tension plug wires could be expected to radiate considerabley more radio frequency interference than the later type system with a mostly metal coil box and shorter high tension wires. Cars with a metal firewall would probably better contain RF radiation from the ignition.

[Luke]

Dave,

From reading your posts I doubt, as others have said, that the issue you have results specifically from the timer or mag.

It is possible however that you have introduced some sort of grounding issue, either with the indicator cct, or with the engine. To eliminate (or fix!) that I suggest thoroughly checking any engine/body/chassis connections you have, you may find one or more missing, or have a high-resistance joint.

Related to this; when there's a lot of RF around it's possible for poor connections to effectively rectify and create a small power source (voltage) where it's not wanted. Given the more sensitive LED system you're using something like this could well be responsible for what you're experiencing.

Although it wouldn't deal with the source of the issue another way of possibly 'fixing' the problem would be to install some 0.1uf capacitors between ground and each wire of the indicator cct - including, or even starting with, the power feed. These should effectively short out any stray RF to ground and may permit the system to operate normally. That said it would be preferable to also try and sort out the originating problem - obviously you can try grounding and/or capacitor installation with the engine running and the system faulting, in order to see if any of these things will make a difference. Note that a poor power feed connection within the indicator cct could also produce a similar result, it's not just ground connections that might cause it although they're more likely for various reasons.

BTW do NOT ground the magneto output!

Luke.

[Dave Young]

Thanks, Luke. Come to think of it, I did have a ground cable from the engine to the frame before doing the engine swap. I have rubber bushings between the body and the frame and also on the engine mounts. I put a ground back on it and see what happens.

[Dave Young]

“I’ll put a ground back on”

[Dave Young]

I finally resolved this issue by installing a new flasher. Nothing else made any difference.

[Luke]

I finally resolved this issue by installing a new flasher. Nothing else made any difference.

Thanks for updating, was the new unit the same make/model?

Luke.