Led flasher in '40 ford

[mike in las vegas]

I have the same problem with the exact set up. I haven't tried to fix yet but my thoughs are that our cars have a ton of EMF. Ignition and charging systems. Ground being good because the lights blink normal with car not running. I want to try a condenser ie capacitor at the flash can unit. All I will try is a old points condenser and see if it works. Any othe thoughts controlling EMF would be appriciated.