I have one really grotty, nasty charger which makes the same problem, other chargers (like USB from PC) are ok.
Maybe the direct-current from your charger is too unstable and disturbing the touch input, I also read about in a computer magazin once.
(german article)
Even unlocking the screen usually doesn’t work (as in, I cannot slide the lock button up to enter the PIN).
Hmm… I’m using the same charger as witht he old phone, I’ll have to try another one, thanks!
What this means exactly? You make the swipe an the touch screen do not follow your movement?
Or is the necassary space covered by any other part of the software?
From your explanation it is not quite clear, what your exact problem is…
I second this, I’ve had the same problem with my FP2 at first using a chinese plug, but lower-amperage plugs proved to be ok with me.
I have this problem using a usb charger… If I use my old Samsung S2 charger then it works fine.
Ah, excellent! I experienced this yesterday when I was charging my FP2. Touchscreen was completely unusable. I was afraid it might be a general problem, but if it is related to the charger, then I’m quite relieved 
I just found myself/ my phone with the same problem - the touchscreen is completely useless while charging. Actually, this is already the second charger I am trying as the first one did not charge the phone at all. I guess this will take some experimenting to find out which charger works best. I wonder whether this makes the case for a FP specific charger, or we simply need to be happy that all of us have several of these at home?
I still don’t get what you mean by “unusable”? Does the touchscreen not respond at all or does it misinterpret the touch inputs.
In the latter case it’s a known bug:
@paulakreuzer I don’t get the random inputs as described in this other threat. Only when my charger is connected, the touchpad goes haywire. In the upper half of the screen each tip is about 3 cm off, so its hard to hit anything and impossible for some screen areas. In the lower part of the screen, as soon as I touch it, it starts scrolling madly in all kinds of directions and I just see letters flying by if there is a lot of text on the screen. disconnect the charger, switch screen off and on once and everything works fine again…
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Oh ok so it’s the same symptoms as the other issue, just only while charging and locked.
Then I guess the only fix will be to try other cables/chargers/usb-slots/sockets…
The cable should be a 4 wired data cable (which you can use to transfer data to your computer) and as for the charger you’ll just have to try.
Chargers & Cables that are not 100% compatible can cause static and that can cause aberrant touchscreen behavior.
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issue description
Only when charging, my phones screen freezes, is very unresponsive respectively.
Once I unplug the charger, my phone reacts normal. (i.e. responds to my commands/touches)
When charging
- unlocking the screen does not work satisfactory (screen lock type: swipe)
- several attempts are necessary to unlock the screen
(I need to press the power button -> black screen.
press power button again --> lock screen --> unlocking the screen works every once in a while.
If unlocking did not work, I need to get back on black screen and then to lock screen and try again) - once screen is unlocked, the screen freezes randomly again
(while an attempt to open an app, open settings, installing widgets, swiping down to open status bar, etc.) - the power button does the trick again, just to get a screen freeze a few seconds later
When not charging/ charger unplugged
The phone reacts absolutely normal in an instant.
Question
I have not read about the problem in the Forum yet. Anyone phasing the same or a similar issue?
Any suggestions for help are much appreciated.
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I moved your post here as it seems to be the same issue.
Also check this thread:
Does the touch & hold delay workaround described there help?
Thank you paulakreuzer for the very quick response!
I tried your solution ("touch&hold from short to medium) and it seams to work/ it works.
Thank you for that!
I have not tried the solution with another charger.
Seams not useful for my issue anyway.
(As I could always get one step further after going to black screen and back again)
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No, generally, there’s no reaction at all.
However, as per d2w’s suggestion, I borrowed another charger and tested the phone against it, and the problem disappeared, so my charger is at fault. I spent the last four years thinking it’s normal for smart phones to become slower during charging, just not unusable (I guess the charger is getting worse).
Thanks for the help, people!
Hi there!
I experiance excatly the same problems as described by @arise-teamrider.
I then tried the workaround described in the Crazy touch inputs (touchscreen issue). This, however, made the behaviour even worse in my case. The unlocking screen showed really weird phenomenas, like a kind of flickering of large squares.
Also, when i further increase the “touch & hold delay” to long, the problem still persists.
The charger I use is from “Emerson Network Power” and I used it together with my HTC, on which it didn’t cause any problems while charging.
When I use another charger, namely a “Samsung Travel Adapter” (Model: ETA3U30EBE), though, with an output of 4.75V and 0.55A (which is actually not the recommended output of 5V and 1A, like described in the manual), then the problems also persist. But, the problems occur far less often (e.g. when unlocking the screen, about 3 out of 5 times it works, whereas with the HTC charger about 1 out of 6 times i unlocked successfully).
I guess, it would be useful to publish a growing list with FP2 compatible adapters?
It’s great to find help here already, thanks for that!
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I have just received a replacement phone from Fairphone, so until I send it back tomorrow I have two phones. The new one is suffering from the problem mentioned in this thread, it becomes unusable until you unplug the cable. The old one however works fine with the same charger/cable.
Does this mean it’s the phone causing these issues and not the chargers/cables?
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When I charge my phone via the USB port of my computer, everything works fine. On a charger scrolling goes wild, just as described in this thread 
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Sounds like a grounding problem.
The touch screen is looking for your finger to be at the same voltage as most of the phone (which is at the same voltage as you because you’re holding it).
When you plug the phone in to a charger, the voltage of the phone changes to the “ground” voltage of what the charger is plugged into. Now the screen doesn’t see the phone at the same voltage as your finger and refuses to work. Some chargers are isolated (so the phone doesn’t get grounded) and some are not. The work around is to ground yourself as well!! Touch something that is earthed … like the outside of a metal kettle or the edge of a plugged in laptop, and the screen will work … sometimes your body potential will stay at “ground” and the phone will keep working when you disconnect yourself from ground … sometimes not. It depends what you’re standing on (whether you’re wearing socks … standing on damp ground … all sorts).
Had this endlessly with my old mobile and sometimes withe the FP2. It’s physics sadly.
PS it probably works when charging off your pc because the pc is working off batteries or has an isolated power supply. My Dell laptop isn’t isolated btw so if you use it plugged in, with bare feet you get a buzz off it.
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I have the same problem using a Samsung charger (FP2 is unusable during charging).
When changing the charger to another one (Amazon for Kindle) or via usb to computer the phone works fine during charging.
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