Hey, the new sensor will not help you get Face ID back, because it is not paired to the phone. If you want Face ID to work, you have to swap the flood illuminator module over to the new cable. This requires some skill and a hot air gun. Since the professionals in your city cannot help you, you could either send the phone to someone like iPad Rehab /STS Telecom (be sure to tell them that you just need the cable fixed) or install the new cable (keep the old one safe) and live without Face ID for now.
I know this is probably too late, but this is a classic Audio IC failure. As for checking it, there’s really no way to other than ensuring you have good parts. The problems are caused by a broken connection under a chip. Since the pad goes to a tiny resistor, you could try measuring it against a known good board, but there’s really no use. This issue is so widespread that the Audio IC will have a broken pad in 99% of these cases.
The first and second gen screens are not compatible, because the second gen has ProMotion, and the first gen does not. Also, their connectors look different. As for quality, you get what you pay for. I have not bought a screen from iFixit yet (I mostly buy batteries), but they have a very good reputation.
If it is not a software issue ( and you seem to say it is not ), the LCD is probably at fault. Try the software restore first, but if that fails to fix it, you can follow iFixit’s guide to replacing the LCD. I would recommend opening the iPad first and reseating the connector before buying a new LCD to rule out a bad connection.
The only other thing that might help is connecting the phone to a computer with iTunes, and trying to update it using Recovery Mode. See this article for tips on how to enter Recovery Mode: https://support.apple.com/en-us/HT201263. Be warned - clicking Restore will DELETE your DATA! If this does not work, your phone will need to be opened up to be repaired. Follow iFixit’s iPhone 7 Logic Board Removal guide (iPhone 7 Logic Board Replacement), but you can stop unscrewing components after step 24. Instead, simply disconnect everything from the logic board but the power button cable, the display, and the battery. This will determine if a faulty camera/earpiece cable ( a fairly common problem for this generation of iPhone ) is causing your problem. Best of Luck!
That’s definitely a shorted component. :( I have a 7 that I am concerned is overheating but it rarely ever gives the temperature warning. What I would do is boot the phone with screen, battery, and logic board only to see which area gets hot. Then use a multimeter to determine if any power lines are shorted. Don’t get fooled if something like the PMIC gets hot; this is due to something else shorting a power line 99% of the time. Alcohol also really helps in these cases, especially because it it outputting a lot of heat. Once you find the source of the short, it really depends on what is causing it. If it is a capacitor on a big power line (with many others also on that line), you can just yeet it off with tweezers or an exacto knife (being gentle obviously). If it is a chip, the phone will probably need micro soldering work. Best of luck!
This definitely seems like a sensors issue. It wouldn’t hurt to try removing your motherboard and checking for water damage, but I doubt that it will be enough to fix it. You don’t have to replace the logic board; there are many reputable microsolderers out there. Louis Rossmann has a video about this exact issue, so he could definitely help. Also, iPad Rehab has some very smart people, but I don’t know if they work on macs.
Hi, the baseband CPU, the baseband EEPROM, the logic EEPROM, and the WiFi chip have to be swapped as well. The logic EEPROM can be left out if you don’t mind erasing the phone, and the WiFi can be left out if you have a NAND programmer. Be warned: this is VERY difficult!