[AC Question]

My Galaxy S4 touchscreen suddenly stopped working yesterday. the power button brought up the lighted screen, but screen was non responsive to touch, and I could not unlock the phone. All functions of the phone seem to be working, as I get sound notification of texts and emails, and the status bar shows notifications. I can also make & receive calls from my car's handsfree, and take incoming calls on the phone itself with the voice recognition "answer" command. So it seems the phone is working fine...just a non-responsive touch screen.
I tried a few "soft resets", removing the battery from the phone while on, pressing the poser button for at least a minute, and then replacing the battery and restarting. No luck. Overnight, I let the battery run down to very little, and VERY BRIEFLY the touchpad was working again. I think I unlocked the phone, looked at email without opening a message, and looked to see FB notifications before the screen went dead again -- so, very few commands and then non-working again.
I have removed the 16gb card for external storage, and am thinking about a hard reset -- power button, volume button and home button pushed simultaneously to clear the cache. But before I do that I want to back up the info on the phone. The phone memory says it has 1.7gb free, and about __ used. I am at a loss to see where all that used space is, because if I click the folders one by one, there doesn't seem to be any big storage that I can see -- just a few KB or MB in various files.
I don't really want to do the hard reset, because I like to keep my texts...but maybe that is why the cache is so full. Is there any way to get the texts off and save or restore them? Also, am I on the right track about the touchscreen issue being caused by the too full cache? Any suggestions?
I was so frustrated I called a highly reviewed cell repair shop here in Tucson, and they flatly said the phone needed a new touchscreen, it didn't have anything to do with data or the cache. Just so you know the facts, the phone did have the screen replaced with a genuine Samsung screen in Sept 2015, but there have been no problems since that miraculous repair.
Again, any suggestions or ideas...?

[anon(632115)]

The update file is likely to be occupying a large chunk of space in cache. Turning to the screen it's a bit concerning that they gave a diagnosis without examining the device. Loose connection perhaps. If you can get that phone to connect to Samsung Smart Switch you can do an emergency firmware recovery and data recovery but you have to get it into download mode for that.

[NotherS4User]

I am now a registered user and I posted this question...so to reply
By the update file do you mean the wdh_update file? When I click on properties for this file it says it has zero folders and files and 0 bytes. Maybe I can't see the files properly because I am using Explorer to look at the phone as a drive?
I don't have Smart Switch on the phone, but can maybe load it from a pc or tablet. I was able to load a "SMS Backup & restore" program to the phone remotely from the PC, but can't open the app or get it to work without the touchscreen.
What do you think about the hard reset possibly "fixing" the touchscreen issue?

[anon(632115)]

Does the screen display if you boot into download mode Boot Samsung Galaxy S4 into Recovery and Download Mode