replaced screen now having issues :( galaxy s4 i9505 Good afternoon guys and gals please bear with me as i'm new to this forum anywho i've recently replaced my screen on my galaxy s4 after attempting to replace just the shattered glass and failed! went to go power on the phone for the first time with the new screen and everything was great............................................. .................... for about 5 minutes the screen has freaked out big time on the odd occasion will display properly most of the time its just freaking out. Ive managed to do a factory reset using the android device manager and that seemed to help it out for 10 minutes until it returned to freaking out. Could this be software related? As it booted up fine before the freaking out and is still allowing me to use the touch screen as i can hear the phone unlock. Or should i be contacting the person i got the screen from asking for my money back? My phone was completely fine running wise until i had to change over the screen. i hope you guys canhelp me out as im stuck in a rut as to what to do

galaxy s4 i9505 international variant running stock touchwiz
Your display issue is almost certainly a bad connection on one of the ribbon cables that connect the display to the circuit board.  One of the two cables you had to disconnect didn't get fully seated in the connector, leaving some traces intermittent.  Assuming the connector wasn't damaged when you disconnected the old screen, you may be able to restore correct operation by disassembling to the point where you disconnected the screen and digitizer cables, then carefully following instructions to reconnect those ribbons, followed by completing the reassembly.

You should also be able to install the battery and power up the phone to check things before fully reassembling, which will save time if you have to take several tries to get a good connection.