This is part of why we are here - to learn new skills from each other

They're only diodes when all said and done Rod😉
One lives and learns 😎

44yr in electronics & I learned something from this discussion today. Hav never used the diode test function of my multimeter on anything but 1n4148 signal diodes. Didn't know you cud find out so much abt an LED that way.

thanks thats a great help well done all

Longest wire out of bulb is positive and if you get wires wrong way round LED won't light, if its wrong voltage it will either light ok or light Dimly or just burn out quick👍👍

https://www.wikihow.com/Test-LED-Lights

This article covers two ways to do it

At last, the right question Dave👍
Doug😎

Hi Stephen can you post a pic of the Leds you are using, please?
dave976

In lieu of heatshrink tubing you can use a brush-on insulating coating which is sold for automotive & marine use & often used to dip tool handles to insulate them. I get mine at PRINCESS AUTO. The lid includes a brush immersed in the stuff.

Don't apply a battery directly to the LED, it will destroy it. You need a current-limiting resistor, occasionally referred to as a ballast resistor, I wud suggest a minimum of 68 Ohms or 100 Ohms. That's for a quick test. For a permanent installation you will want to select the resistor value to give you the desired brightness.

Red LEDs require the least voltage, other colours require more, & a white LED needs a bit over 4V to "ignite".

Simy put, if both wires are same colour, if they don't work one direction, reverse your wires.
Some LEDs have one wire longer than the other.- longer lead is often the pos.
The wires can usually be stripped with a thumbnail or small blade.
I solder the leads, then cover with small heat shrink tubing.

Some wires you can strip by dipping in acetone which you can buy in small bottles in the dollar store.

If they are new the longer leg is positive!

Hi Stephen, I use these wire strippers. They work on all wire sizes and are readily available at a hardware store. As far as testing an LED I use a 1.5V AA battery. Hook the wires one way, if it doesn't light up reverse the wires and it will light up. Then mark your pos and neg wires. This is kind of primitive but will not damage the LED. I always solder all the connections. Don't forget to put heat shrink on before you solder the wires. Hope this helps...RR