ac mag current "leaking" into dc battery current?

[bobt]

Hello. I have a 1915 touring non starter, non generator. I start the car on battery then switch to magneto. I'm using a 12 volt garden tractor battery that I use a battery tender on. I'm happy with the way my car starts and runs and I drive EVERY day. OK, now I ordered a 12 volt flashing LED amber light and mounted it on the rear of the car because I putt around town and don't want to get rear-ended. I wired the light on a new single circuit on the BATTERY side that consists of a fuse, a switch and wire and it works GREAT as long as the cars not running. when I turn the light on, it flashes about once per second which is perfect. As soon as I start the engine, the light goes into a disco strobe effect no matter what side the ignition switch is turned to ( bat or mag). I'm thinking that my ignition switch might be the problem? It's a normal Ford switch. Any ideas, Thanks, bobt

[bobt]

Oh yeah, By the way. The light will go to the strobe effect WITHOUT the engine running if a coil is buzzing on battery position. ??? bobt

[Squirrel]

You might read the instruction manual for the light. It could be that it has a "low battery warning" feature, that makes it flash quickly, when the battery voltage drops below a certain level...and that level would be hit whenever there is a load on the battery, such as an ignition coil.

If you have an accurate volt meter, you can measure the voltage to the light.

Since the light acts up when the engine is not running, it's unlikely that mag voltage is somehow leaking into the battery circuit.

[Mark Gregush]

I don't think it is the switch. I would suggest trying this; mount the light so it is not using the chassis as a ground. Run a ground wire from the battery to it. LED's may be more sensitive to interference then a regular bulb so may be picking up the AC signal through ground. I am thinking that most that use these light, use the self contained battery powered ones so this may not be an issue, so has not been talked about.

[TRDxB2]

Need to know exactly what product you purchased. In checking to see what you might have - most were described as having a "triple-flash strobe pattern". I found some information indicating flashing (solid, left-right, top-bottom, in-out and solid) and some instructions for wiring https://www.whelen.com/install/144/14435.pdf There is a warning at the bottom of these instructions, may apply to your device or not "Therefore, after installation of any electronic device it is necessary to test all electronic equipment simultaneously to insure that they operate free of interference from other components within the vehicle. Never power emergency warning equipment from the same circuit or share the same grounding circuit with radio communication equipment." How did your wire it up?

[Novice]

bobt. The model T buzzer coils are in effect a spark transmitter similar to what was used in the early days of radio transmission by radio hobbyists.What You need is a rf filter like the ones they used to put on car generator's. a capacitor to ground across the led may do the trick or You may need more filtering with a rf choke coil/ transformer and capacitor to remove the rf/ac generated by the buzzer coils off the 12 volt line from the battery.

[Altair]

I think it has been mostly summed up I think generally your lights are not compatible with your power supply. My grandson installed some very expensive LED headlights in hid Ford Ranger and all they did was flash (very fast) and were excessively bright. He was forced to revert back to the stock lights. They weren't compatible with his electrical system.

[Mark Gregush]

I have LED tail/brake lights and separate standard bulb turn signals with the old style flasher. My brake and tail lights are fine till I use the turn signal. Then the tail lights and brake lights when activated on both sides has a flicker. It's not bad enough to fuss with, so I will live with it.