That might be the case, otherwise you may need to do a full screen replacement. The screen replacement guide on Ifixit.com will show which cables should be connected and if neither of those suggestions work, it’s a motherboard issue, and not cost effective to repair, in my opinion.
You may have blown the backlight out. If you repair phones try a different screen, if that doesn’t fix the issue, then my guess is it’s a mother board issue that would need microsoldering. Also, if you download a program 3utools from 3u.com, that program tells you basic problems with your device.
Really? Because I called the company I buy my parts from, and online I am getting conflicting answers as well, and I am getting so aggravated, because the guy who has my watch is in CA, and is not responding, and now I have a screen on the way that is both gps and lte and a watch I could get with a cracked screen that is only gps for 110, so in total I would be paying 175 for a series 3………this is driving me bonkers!!!
You have to make sure you change the logic board (motherboard) with an iCloud UNLOCKED logic board that includes the original home button for that particular logic board, or your touch ID won't function correctly. Also, this may sound like a dumb question, but have you changed the battery yet?