Introduction
All electronic devices generate heat. This is a fact of science. But if they are hotter than normal, touching your phone is uncomfortable, or a thermal warning shows on screen, this could be cause for concern. With any luck, the fixes on this page will have your phone running cool as a cucumber.
First Steps
Before undertaking any of the more time-consuming solutions below, these are a few fundamentals to give a go.
- It is normal for your device to be warmer than usual when restoring from a backup, updating the software, playing a game, or charging.
- Move to a cooler environment. It may just be that a high ambient temperature is forcing a hotter internal temperature. Turn the device off and wait for it to cool. Avoid putting it in the fridge or freezer. Thermal shock can cause cracks to the front or rear glass and rapid cooling attracts condensation.
- If you're charging, remove it from the charger, particularly if you are charging wirelessly. Wireless charging is less efficient and therefore generates more heat as a byproduct.
- Close high power consumption apps like GPS, games, or cloud sync services.
- Update your software. A newer version of iOS or a third-party app could be poorly optimized and an update may resolve this.
Causes
Phones are devices with very little headroom to dissipate the heat they generate. Think about a computer, which likely has at least a single fan to move air around inside. iPhones don’t have room for this sort of cooling and must relieve thermal buildup passively.
- Remove your case, especially if it is one that envelopes the entire phone. It could be trapping heat in.
- Open your phone to check for dust build-up on the internals. Use compressed air, or a cotton swab with isopropyl alcohol to remove it.
- The chances of this causing overheating are slim, but if you spend a significant amount of time in dusty environments, it is worth exploring.
Batteries are one of the major sources of heat in a phone due to the constant energy exchange within them. If your battery is failing, or at the end of its life, it may generate more heat than normal.
- Check your battery health. Under Settings > Battery > Battery Health, does it say Service?
- By Apple’s guidelines, anything with a capacity of less than 80% needs battery service, though it can detect other failures as well. If it says Service here, a new battery is a reasonable start.
- Search for signs of battery swelling. Is there localized screen discoloration on the left side (or right side for series 12 and 13 iPhones). Is the screen lifting along one side?
- Replace the battery if there are any indications of failure. Exercise caution when handling the battery—lithium-ion batteries can be hazardous if they are damaged.
In order for you to get an overheating warning, something in your iPhone has to know the temperature exceeds expectations. iPhones are littered with thermistors that communicate temperature.
- Sensors on the charge port assembly are a common trigger. Open your device and unplug your charge port from the logic board. Reference the repair guide for your phone if you're not sure which cable this is. Power it up and see if you still get a warning. Replace the charge port assembly if this resolves the issue. Note: Most iPhones will restart after three minutes when this cable is disconnected. This is expected behavior.
- The camera flash also contains a thermal sensor. The placement of the flash varies but is often part of the power button flex. Check its location on your specific model by perusing the Apple iPhone Parts or checking out the iPhone guides for your model. Use the same cable disconnection method for verification. Note: If the flash is on the power button flex, connect the phone to a charger to power it on.
Find compatible replacement parts for your iPhone. All parts and fix kits are backed by the iFixit Quality Guarantee.
One of the electrical lines in your phone may have developed a short-to-ground. This simply means that rather than energy being held in its circuit, it is sent straight to the ground.
- This may be the case if your phone got very hot and now will not power on.
- Attempt to find the short by booting on a minimal hardware configuration.
- Open up the device and disconnect anything that is not necessary for you to power the phone on. For most iPhones, this means a battery, a charge port, and a display (so you know it’s booting).
- Connect a charger or USB cable to prompt the phone to boot.
- If the phone boots normally on the minimal setup, reconnect the parts one by one. Power off and disconnect the battery while you connect any additional parts. Be especially suspicious of the home button and front-facing camera cables.
- If the issue reappears after connecting a specific part, replace that one.
- If the issue is still present after this, your issue is likely the board itself.
Ultimately, all the temperature information travels to the logic board. The board is also home to many sensors itself. A poor electrical connection, faulty board sensor, or even a misbehaving chip could be your issue.
- Board-level issues are most easily corrected by replacing the board.
- Contrary to popular belief, the board itself can be repaired. However, it requires specialized tools and microsoldering know-how. This is not something most people can do themselves, but many independent repair shops can do it for you! Ask around to find board-level repair specialists near you.
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