I purchased the Sylvania Zevo LED to replace my 1157 on my 67 Mustang, but they will not blink, however they stay stuck on Bright like they wanted to Blink. Do i need to add a resistor before the light socket? Or add something else?
I did resistors on a '40 as I did the taillights only. After words I found they make special flashers for the LED bulbs, and I think even ones for mixed LED and regular bulbs. The LED's don't draw enough voltage to trip the flasher unit..
Did you see the size of that chicken?! -Dirty Steve
Conventional flashers work on circuit resistance causing a bi-metal strip to heat up and bend, breaking the circuit, then cooling and re-establishing contact. LED's have much less resistance and won't heat the strip enough to bend.
You can either replace the flasher with a solid state unit that doesn't rely on load, or add resistors to make up for the lost load.