Why does my iPhone 3GS have an intermittent white screen?

U have broken ur iphones Display ic in Logic board.

I have the same problem, but it was not resolved by a new screen. When it locks it still goes white. It seems to be set off by squeezing the phone into a holder or pocket too, so probably a dodgy coonction on the main board. As a quick temporary fix you can re-boot the phone, then go straight into settings and set the auto lock (in general settings) to never. The screen will stay on permanently, but the battery runs down in about 14 hours. Dim the screen a bit in settings to stretch this out a bit. Working on a fix as i write.

This just started happening to my 3GS recently. It is very much intermittent. Sometimes I turn it "off" with the top button, wait 10sec, and press either that button or the home button and it will show the normal unlock screen. Seems like 50% chance of good last week, a whole day of 100% good, and 10% today.

The screen is not pure white: it appears off-white with a block of a pastel color.

Thanks for the suggestion of turning off auto-lock; to reduce unintended actions, I am using it with the "status" (weather, stocks, etc) screen that appears after a full downward swipe. Obviously, this is only a temporary workaround.

Intermittent problems can generate endless hypotheses. Since others encountered this about 2 years ago, I can conclude it has nothing to do with a recent update. And since the problem occurs when waking it up via the top button or the home button, the buttons are not to blame. It might be a corroded lcd connection that exhibits hysteresis. Perhaps a lengthy no-autolock On period would help it.

The same thing is happening to my 3gs . I fell over in school ( Im 14) and broke the screen. I bought a new one and it was replaced by my sister (18) . It was then working perfectly . A few weeks later my screen kept flashing white . Another week or so it would go white and come back on in an hour or so I still need to fix myn as well .