Chosen Solution
I bought a water damage iPhone 6. fully functioning but backlight was badly water damaged. Everything still functioned perfectly on the phone except weak wifi signal. I opened up the phone and it was perfect, no signs of water whatsoever and all the indicators were untouched. I was thinking the item I need to replace is the antenna top left of the phone but I can’t actually find what part is causing the problem Does anybody know thanks
Solved by replacing the antenna cable in the top left corner. Logic board needs to be removed as well but when done it’s 5 second job.