Backlight on sidekick 3

Because your screen is broken and that can only be fixed if you have it replaced.

there is a setting on it that makes it so you cant use the back light and i accidently did that but i just went to my settings and turned it back on

Well thats another common problem with the sidekick 3. Your backlight went out. LIke lightbulbs do. Get your screen replaced, or luckily just your backlight replaced

You can test it; put probes on the backlight wires to see if it's being powered and how much, then try an independent supply on a disconnected display to see if it was the connector, backlight, or a driver circuit which failed (assuming you already got under a bright lamp and twiddle the settings to permit backlight toggling, then tried toggling it.)

how do u get it repaced will t-mobile do it?

how do u get it repaced will t-mobile do it

if you change the screens. like get someones sk2 screen and replace it wit yours, thats if they dont want it. thats what my sister did and it works perfectly.