Im in need of a Noid light.. which from my understanding is just a fast reacting test light. I've heard others using regular bulbs and others using led's.
Will a 12v led lite work? like one from a trailer side marker? if its 12v I would guess I wouldnt need a resistor. Am I correct in my assumptions?

 

If you're just looking for something to check to see if there's 12V between two points then any 12V light will work, be it LED or incandescent. As long as you're sure the light is 12V then there's no need for a resistor, so your assumptions would be correct. I made one of these lights awhile ago by just soldering a couple alligator clips onto a spare 12V bulb I had around. If the light isn't 12V then there's ways to still make it work, feel free to post back for a lesson on Ohm's Law.

You're probably better off just spending $5 and getting a cheap DVM (multimeter) as that will do more electrical operations than just the light bulb. Once I got my multimeter, I haven't really had much use for the "noid light" as you call it (I've never heard of a name for it before )

 

Noid light is for checking injectors. A set of noid lights can be bought from Harbor Freight for under $20.

 

I have a test light and a mutlimeter. I wanted something that would show a quick on/off pattern not volts. Ill be using it for testing a fuel injector pulse.

 

Well if all you want is an indicator of a signal then I'd suggest using a LED bulb if possible. Reason being that LEDs turn on and off quicker than incandescent bulbs which may allow you to see the signal better.