Replacing incandescent indicator lights in instrument cluster with leds

[I support common sense]

I tried to replace the indicator lights in my dash with leds, but for what ever reason certain lights would not work, I tried to put them in both ways because an led is polarized and still know difference. It would only work one direction, but sometimes it wouldn’t work. I wondered if it was because of the lack of resistance. The two reasons I tried replacing them were to give it a sharper color, and to ensure I’ll never have to take the dash apart again. Does anyone know more about the cluster, and why incandescents work and leds don’t?

 

[pentode]

What kind of LEDs did you use in there? What year is your truck? As far as I know, all those bulbs are 12v so you'd either need current limiting resistors to keep them from burning out or some kind of LED lighting with built in resistors.