iPhone 5 grey screen even after replacment

Hey,

I have an iPhone 5 that a friend gave me, she would have thrown it away. She replaced it, because she accidentally left it outside in very strong sunlight and the battery bulged. It pressed the screen and the whole phone just came apart. Apart from that the screen started to act weird, it showed grey lines and some parts turned very colorful. Then she tried to take it to a phone service (we don't have Apple Stores here) but she had no luck there, the guys were not very helpful, and they even broke her screen. Then she gave up on it, and just bought a new phone.

So she asked me if I wanted it, otherwise she'll just throw it out. I said yes, why not, I'll try to fix it. I ordered an iFixit kit for a new screen and a battery. I thought that the weird behavior of the screen is just because the battery pulled out some of the connectors of the screen. So I took it apart, repaired it, but when I turn it on, it still does the grey screen thing.

The whole screen turns grey and it doesn't seem to be very responsive. The phone works though. When I long press the home button, Siri answers. And after playing with it for a while, the screen suddenly turns back to normal, and everything works fine. I took a screenshot when it was all grey, and looked at it after it turned back to normal, and the screenshot was perfectly fine, it wasn't grey. So I'm guessing it's not a software issue. Also, after working properly, sometimes parts of the screen turn to weird colors. I made two videos about this problem:

Video 1

Video 2

I hope someone can help me!

Janos

As I still couldn't figure out what the problem is, I'm sending back the repair kit to ifixit.