Screen goes dark after sleep mode.

I've actually had this problem for ages, but someone recently gave me an ifixit kit to repair my battery that wasn't holding a charge so I thought I'd see if I could solve this issue too.

I've had this laptop going on six years. Whenever it goes into sleep mode, my screen goes dark. The power remains on, but the screen is totally black and using the keyboard or mousepad won't bring it out of sleep mode. I have to completely turn it off and on again.

Also, whenever I close the laptop lid the same situation seems to happen. The screen goes dark but the power remains on, so before I noticed it happening my laptop would just sit in my bag overheating while the battery drained. Now I turn my computer completely off whenever I'm done using it.

If anyone can think of a way to fix this, I'd really appreciate it. It would increase the usability of this machine so much.