Backlight will work as long as its half brightness

[ShelbyGT660]

I have a iPhone 3GS 16Gb Black, Its the blue motherboard edition, I purchased two iPhones, 1 3G and another 3GS both 8Gb for parts for this one. I replaced the backing and the screen with the one off the 3G as I was planing on selling the 3GS after I had repaired it. Connected everything and went to turn it on. And i got nothing, so I then googled if the 3G LCD was the same as the 3GS, To find out that it was NOT. So I rushed and disconnected the LCD and digitizer, Grabbed the old LCD and Digitizer, hooked it up, Only to find that it turned on, but the backlight flickered then went out. So i left it for a few days, Came back and the battery was dead. I put it on charge and the "Red Battery" came up in full brightness. So i figured it fixed its self. I was wrong, After it had booted the backlight went out again. After a week of debating what to do, I figured for the hell of it i would restore it. Restored and still just the flicker when turning on or pressing the "standby" button. So I made my way to the settings and turned down the brightness and locked the phone then went to unlock it. backlight WORKS. So i went to turn it up, it makes it to a little under halfway then it dies. The screen is still working just no backlight unless I turn it down and lock and unlock it again. Any suggestions? I have tested the coil with ohms and it has continuity.