iPhone not charging when plugged in?
Once you're certain that it's not an issue with the outlet, charging block or cord— and the phone still isn't charging, then the problem can be reduced down to a few different options: a bad battery, charging port, or tristar.
Any knowledgeable electronics repair shop should be able to pretty quickly determine the source of the issue by observing if the phone draws any current with an ammeter, dry-fitting a new charging port and new battery, and observing the response through the ammeter.
A bad tristar might still result in the phone drawing current, but won't allow the battery to charge. To be certain, a known working battery might be dry-fit onto the phone and if the phone still won't charge the new battery, then a tristar repair is indicated.
So what is a tristar?
A tristar is a chip (1610A3) on the motherboard that recognizes if the phone is plugged in, and addtionally determines if the battery is safe to charge or not. The tristar interfaces with the baseband and functionality of the chip can be definitely tested by using a digital multimeter on the battery terminal to see what voltage the terminal is carrying when the phone is plugged in. With a working tristar, the terminal might be carrying 3.6-4.2v, but a bad tristar will be indicated by 2v or less at the terminal.
What causes a tristar to go bad?
Typically, charging your iPhone using a third party charger or lightning cable that is not Apple MFI certified allows for larger variables in voltage and current, this then damages the tristar chip and can leave you with a seemingly dead/not charging iPhone. Lightning cables actually have a chip in them that regulate the voltage and current being pushed through into the charging port.
Another common reason for this is also charging your iPhone from the cigarette lighter of your car. This does not regulate the voltage as well as the original AC adapter, since alternatively the power is coming from the alternator. If you need to charge your iPhone or any electrical equipment in your car we would recommend a good quality inverter with your original charger and Apple lightning cable.
Fortunately for you, microsoldering techs at Wires Computing do this repair daily with essentially a 99% rate of successful repair. Send yours in today.