No Display After Screen Repair, Phone Still On

Question

iPhone 12 Pro Max

Apple's top-of-the-line smartphone for 2020. Announced on October 13th and released November 13th, the iPhone 12 Pro Max sports a 6.7" OLED display, a triple rear camera system with LiDAR, and 5G connectivity. Successor to the iPhone 11 Pro Max.

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Marcel Nour @marcelnour

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crwdns2931729:0crwdne2931729:0: Mud 26, 2025

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No Display After Screen Repair, Phone Still On

Hi,

I tried replacing the screen on an iPhone 12 Pro Max. After the repair, Face ID wasn’t working, so I opened the phone again to check things.

I noticed the proximity sensor cable had a cut, so I tried taping it as a temporary fix and reconnected everything.

Now, when I turn the phone on, it vibrates, makes sounds, and the backlight turns on, but nothing shows on the screen. It stays completely black with no image at all.

I’ve tried both the original screen and the new replacement screen, and the result is the same — backlight works, but no display.

What could be the issue?

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score 1 · Answer 1 · 2025-05-26T10:31:30-07:00

I'm not sure exactly what's going on with your phone, but let me clear up a couple of items.

First of all, if you've damaged the flex cable going to the proximity sensor, that same cable also feeds the flood illuminator, which is part of the Face ID system (the proximity sensor isn't part of Face ID). If that part is damaged or replaced then Face ID will not work again unless it is replaced by Apple, or you can use the self repair program which may save you a little money; not enough to be worthwhile though. Apple doesn't replace the front sensor assembly by itself; rather if it needs a new one the only way to do that is to buy a new screen from Apple, which comes with the front sensor assembly.

The second thing I wanted to address is your idea that the backlight is working but nothing else. That's incorrect, as your phone has an OLED display, not an LCD. The difference is that in an LCD display, each pixel open or closes to let light through, but needs a light source; i.e., a backlight. On an OLED screen each pixel is an LED, which generates its own light so no separate source is required.

So if you're seeing any kind of light on the screen then the display is at least partially working, but something else seems to be keeping it from coming on.

The admonition to unplug the battery first and plug it in last is always a good idea, but not as critical as it was with an LCD screen. On a display with a backlight there are generally higher voltages and more current flowing to it that can easily short out when trying to connect the display. It wasn't at all unusual to blow out a fuse or a circuit on an LCD display if done with the battery connected, which is why it's vital to make sure it's not plugged in when messing with the screen. As I said, it's still a good idea but not usually a death sentence on an OLED display.

@flannelist Alisha, do you have any ideas here that might help Marcel?

Leooooo1061 @leooooooooo crwdns2934065:0crwdne2934065:0: 512 6 · Answer 2 · 2025-05-26T07:34:49-07:00

Leooooo1061 @leooooooooo

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6

crwdns2931729:0crwdne2931729:0: Mud 26, 2025

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Did you disconnect the battery when working inside? If you din't, then there's a very high chance you'll short components like resistors and fry something that is critical for a phone to work, like the chips that controls the output on the screen.

If you did disconnect the battery, however, I have no idea why the screen won't work - never encountered that issue. However, I did have the same problem as you on the matter of the Face ID on an iPhone X. I took it apart, tried to replace the whole casing, did everything perfectly and carefully, and when I reassembled it the Face ID just crapped out. That thing is seriously delicate and fragile.

In your case though, it's probably the proximity sensor. The phone relies on it to measure the distance of your face to the Face ID module to get an accurate reading, and if you did tore the cables then that could be why Face ID won't work, and not a problem with the Face ID module itself.
As to the screen, I'm not sure what the issue is. Maybe you should clean the press connectors or check both screens' flex cable for tears or cuts. I still have no clue what the issue is after looking through the internet. If you reconnected the screen when it's powered on though, then it won't work; you'll have to restart it.

Hope this helps!

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Thank you!

Im not sure but it could be that i worked inside the phone, without disconnecting the battery. Do i have to remove the battery as the first thing, and then reconnect it as the last thing?

As for the proximty sensor - can i do a regular swap and make it all work again? Or do i have to go some complex way by programming and soldering?

is it possible to see if the device is shorted? Maybe by using a voltmeter, if yes, what part do i have to check for volt?

crwdns2934271:0Mud 26, 2025crwdnd2934271:0 Marcel Nour crwdne2934271:0

Yes, it would be ideal to disconnect the battery first and reconnect it last as you could poke some components and short things easily. However, if the phone powers on and displays nothing, then it might be some other issues, like torn screen cables. @dadibrokeit 's answer might be helpful, as he had provided a lot of information that I didn't. The flood illuminator is indeed on the proximity sensor flex cable, which is paired with the motherboard when it rolled out of the factory, so you might need some highly-skilled people to fix the tear in the cable. @dadibrokeit is also right about the screen; it is OLED and have no backlight. The reason why it is not displaying anything could be very possibly caused by torn cables, as the screen can register the signal telling it to light up but not the ones that tells it to display stuff. Try using Siri to increase the screen brightness and see if it changes. If so, then the screen is probably broken.

crwdns2934271:0Mud 27, 2025crwdnd2934271:0 Leooooo1061 crwdne2934271:0

However if both screens did not work then it might be motherboard related issues. Have you ever dropped the phone before? The motherboard have two layers, and a drop could disconnect the solder in between and cause the screen to malfunction. I used to have an iPhone X that had the exact same issue; screen would light up and display nothing. Took it to a repair shop and they resoldered the boards together and everything is back to normal. Did you poke anything with a screwdriver or metal object while working In the phone? That could also be the problem. I'm not really sure how to check the voltage and stuff(I'm not that highly skilled), but I suggest you to take it to a repair shop. It is best to leave motherboard-level repairs to the professionals. They know how to handle a hot air gun.

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iPhone 12 Pro Max

No Display After Screen Repair, Phone Still On

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