This is the car charger for my iPhone. The yellow swirls light up when it is working. That happens only intermittently. I decided to see what could be done.
Step 1: Open the Case
I cut around the top end of the charger with an abrasive cutting wheel on a Dremel tool. See the dotted yellow line I added to the photo.
Knife for stripping wire
Hot glue gun
Step 2: What I Found Inside
The pliers grip a small steel spring that should be soldered to the circuit board and touches spring clip that grips the sides of the cigarette lighter socket. The small steel spring broke away from the circuit board as soon as I pressed on it to bend it a little. If the small steel spring overheated a little, it would lose its temper and would not make good contact with the spring clip. Somehow, the contact between the small steel spring and the spring clip was not as good as it should be, and this is why my charger worked only sometimes.
Step 3: Does It Still Work?
I connected the alligator clips from a 12 volt charger to see if the LED still lights. The car charger still works.
Step 4: The Plan
I decided to solder a flexible jumper wire between the circuit board and the spring clip. All that needs to be done is to stuff the assembly back into its case.
Step 5: Change of Plans
The spring clip would not slip into the charger's case because the circuit board kept it from compressing enough. I had to insert the spring clip into the case and then insert the circuit board. But, things began to go wrong. First, the jumper wire I used took too much space and I had trouble stuffing the circuit board into the case. Perhaps things would have been different if I had used magnet wire. Then the jumper wire broke off at the circuit board. It should have been simple to solder the jumper wire back in place.
Step 6: Victory After an Apparent Failure
I connected a 12 volt power supply to the power adapter after resoldering the wire, but the LED did not light. I assumed the power adapter no longer worked. I believed I may have gotten a diode too hot by using to large a soldering iron. See the little black rectangle at the top of the circuit board in the photo.
Later I decided to check my assumptions. The little black rectangle is, indeed, a diode; but, it tested as good. I connected my 12 volt power supply again and tested the output leads from the circuit board. To my surprise the power adapter works and puts out 5 volts DC. So, I wicked away solder from the circuit board and set the original spring in place to solder it. My power adapter works. I put everything back into the case and sealed it with hot glue. See the second photo. The problem seems to have been that the little spring was poorly soldered in place from the factory.
It really does not matter that the LED does not work. A lightning bolt appears on the phone's battery symbol when the battery is charging, so the LED is not critical. Perhaps some static electricity generated by handling the charger ruined the LED.