No service after screen replacement.

"Hi everyone,

Sorry for my english if I make mistakes, I'm french, and still learning even if my wife is english ;).

So I had the No service problem after replacing the LCD screen on an iPhone 4S and the Simcard seemed not to be recognized anymore. I checked everything I read in comments of differents questions about this problem people asked on iFixit.

Everyhting was connected correctly, I didn't break the litlle blue coil etc... After a long long night searching, I found where was the problem.

The little black pressure contact underneath the battery connector was not ""high"" enough. I don't really know if you gonna get what I try to explain but I try. This pressure contact has to touch the back cover of the iPhone where there's a metal part who's connected by the two screws to the external antennas of the iPhone. So I just put a little more up this part for that to touch the back cover when you close it.

In the end I recovered the signal and everything works well now.

I'll put some photos if any of you need some and hope that can help you! ;)"

Sounds like you may have knocked off the signal resistor off of the logic board when you was disconnecting a connector.

i had to replace the motherboard. Works great now.

Would soldering the 2 points where the resistor was work like on the iPhone 4?

In theory yes, but I did a beautiful solder on mine under a magnifying glass. The battery percentage wasn't reading right and like I said before, I had a carrier problem after soldering. My guess is some kind of interference or short circuit in the motherboard. So like LEE FORGET suggested I replaced the motherboard. Down here in Brazil the mother board cost me 50% of the original iphone price. But I figured it was better to fix it than let it go to waste. Working fine now.