Digitizer not working but lcd works fine

A cstomer brought me a damaged iphone 4 screen to replace. Lcd was badly cracked and there was no response on the digitizer on the "original" damaged screen.

I assumed this was just a result of phone dropped and cracked screen

replaced the digitizer/lcd assembly and phone booted fine. Just no response from digitizer still. Tried 3 other digitizer assemblies and still no response from digitizer.

Tried a hard reset. Board does not appear to have any damage to it. And the connector on board seems normal.

Any suggestions?

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What kind of tests did you do to determine that the logic board is fine? If the problem doesn't like in the part itself it sounds like the issue is somewhere on the logic board: either the socket or the touchscreen controller itself.


Hello Im am having the exact problem with my iphone 4.


I didn't test the board but said the board does not "appear" to have any damage (meaning cracks or breaks). The connector for the digitizer seems okay. The contacts do not seem damaged. Not sure how to test a board on the circuit level for digitizer activity. But I know the digitizers I used are fine as they work on other boards.

My conclusion was that some place on the board is causing an issue. Never had this before so not exactly sure where to start for testing trial and error.

Is there something or some place on the main board that I should be looking for if there is no touch response... since the digitizers work fine in other iPhone 4 boards?


The iPhone 4 uses a TI 343S0499 IC for its touch screen controller. You may have problems with that. Check for a datasheet, and see what measurements you need to have to ensure it functions. The IC is readily available and will require a reball when exchanged. Hope this helps, good luck.


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