I can't get the fuel cheat.

[FinnGaming]

When i do ALT+F12 it dose noting so i wood like some help.

[kreutzkevic]

What operating system do you use? Windows? MacOS? Linux?

from the wiki:

Edited August 13, 2015 by kreutzkevic

[Gaarst]

On some computers (mostly laptops I guess) there is a key called "fn" (or whatever stands for "function") that you need to press to activate the F## keys in KSP. Then, you'd have to press Fn+Alt+F12 to get the debug menu.

[cantab]

Playing through Steam? You may need to disable the Steam Overlay and Steam Screenshots for KSP.

[Tex_NL]

Three answers. All three correct but none an answer to the OP question.

When i do ALT+F12 ...

To enable infinite fuel you'll have to launch your ship like normal from the SPH/VAB. When your craft is loaded on the runway/launchpad you press and hold Alt, then press F12.

Now a new window will appear allowing you to enable, among several other cheats, infinite fuel. Alt + F12 again will hide the menu again.

Alt + F12 will also work in the SPH/VAB and will allow you different cheats but not infinite fuel.

Edited August 13, 2015 by Tex_NL

[Padishar]

Three answers. All three correct but none an answer to the OP question.

Errr, which question are you referring to? There isn't a question in this thread's OP. Given that he says that Alt-F12 does not(h)ing I would say all three of the previous answers are more likely to be relevant than yours is...

[jackboy900]

When i do ALT+F12 it dose noting so i wood like some help.

I'm presuming english isn't your first language so the spelling is a bit off, here is the correct version:

When i do ALT+F12 it does nothing so i would like some help, please.

Also are you

1. Launched (outside VAB/SPH)

2. Holding Alt + F12 together

3. On windows (if not the Option key for Mac or L shift/Win for linux)

4. Holding Fn down (if it is needed if you are on laptop)

5. Have steam overlay disabled (maybe hijacking you F keys if you use steam)

6. Is the window opening and you're clicking on the button (if not click on it)

7. Have the window open on the cheats tab (if not then it should be cheats)

If all these are Yes then file a bug report