Just refer to the solution below and do some check up on the highlighted components.
Samsung Gt-I9300 Touchscreen S3 Ways
First Try To Check The Touchscreen Flexi Cable Connection And Check If There Are Broken Or Damaged Its Touchscreen Cable
Ic Rehot His Second Touch Touchscreen That Is Its Flexi Kabek
Try Changing Its Touchscreen
If It Is Still Good … Check One By One Lane Its Touchscreen
See The Image Below:
Samsung GT-I9300 Touchscreen Jumper Ways
Samsung S3 I9300 Touch Not Working Problem Repair
Samsung I9300 Touch Screen Ic Location Solution Ways Track Path
Hints on troubleshooting touch screen failure on Samsung S3 I9300:
This will work if you already tried replacing the touch screen module and restoring the device firmware.
1.Check/clean the touch screen pin connector, re-solder it if necessary.
2. Check/read the touch screen supply voltage (VIO 1.8V) across to the filter coil.
If the voltage is missing check/replace the 0 ohms resistor, or apply a jumper if the line paths is open or cut.
3. Trace the RESET and PINT DAV line paths. apply a jumper if connection is open or cut.
4. Rework, re-ball or replace the Touch Controller chip.