I have a iPhone 6s and when i leave it the WiFi goes and turns to 3G then when you press the side button or home button the

screen lights and you see the 3G go and the WiFi bars turn from grey to white to say it active.

No power saving mode on/apps only update when WiFi signal so im a bit confused as 2 others friends iPhone 6 stops with WiFi signal.

Is it a setting somewhere.

Do you have WiFi assist turned on? Then can cause the phone to automatically change between WiFi and 3G/4G depending on signal strength. Don't know why it would change when screen is locked/ unlocked though?

3 hours ago, mike6688 said:

Do you have WiFi assist turned on? Then can cause the phone to automatically change between WiFi and 3G/4G depending on signal strength. Don't know why it would change when screen is locked/ unlocked though?

Where is the wifi assist,i have just looked at it again and when locked and screen off it  sits idle just 3g,hit home or side wake button and the

wifi comes on grey then full,its bad on itunes to work off wifi as it keeps going off wifi so shows no phone.

Edited July 29, 20178 yr by jace1969
Found wifi assist and already off.

Been told its nothing to do with phone its the router as all phones will connect to WiFi if password is in and setting are set to.

None go into stand by off WiFi onto 3g/4g.         Mine does

Wifi assist is in settings then mobile data right at the bottom make sure it's off saves your data and battery


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I'm going to back up the comments made by @mike6688 & @Philf1 it will be your phone. Check the wifi assist as above, job done.


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Yeah the phone will connect automaically to the WiFi if it's one connected to before. The router wouldn't be able to turn on or off the wifi on the phone when locked or unlocked though. Do you have other devices connecting to the router? Perhaps if there are a large number of devices connecting; then router can't handle the load and the connection to your phone is dropped as it senses the phone is no longer trying to receive anything from the wifi when locked? 

I have just solved it and its weird how its worked,the assist was always off as i only wanted it to update on WiFi but this is what i did.

I run off 2G and 5G so the better signal works and if none turns to 3g but turned apps off what i don't want to use mobile data so WiFi or nothing, i have had it always set like this.

So i deleted my 2G WiFi on my phone so it would only work off 5G and no change still did it so reset all WiFi and searched then put 5G password in and 2G so back to as it was and seemed to work ok and stopped on even when locked so just gone back to the same,weird but worked.                                        

How many people run there phones off 5g if they have it,i have found i hope that when mine is on 5g and still a 100% signal it drops it on my phone so had to go to 2g being it gives a better range,this is the only thing i think the problem is as it did switch from 5g to 2g but don't now for some reason and i have been through every setting that it could be.

Also is there a good forum just for apple but not official one.

Does any have this problem on there iPhone,6,6s or 7 or even working on 10.3.3 Firmware.

Been told its router disconnecting when on a locked screen,nothing on phone as been checked and all 100% fine and setting.

Phone it locked and screen off,hit Home button or side button and lights up and no WiFi just 3G then you see it connect,don't unlock it.