In this case study, we have a MacBook Air 13" 2015 A1466 model, board number 820-00165, which stopped turning on randomly one day, but was still showing a charger light. The customer reported a 'Service Battery' warning, which had been present roughly a year before the device completely stopped turning on.
Disassembling the device, there were no immediate signs of physical or liquid damage, the device looked clean and like it was well looked after. We started measuring through voltages to find out what exactly is preventing the MacBook from booting, since it was likely missing a required voltage, or one was lower than normal. We found PPBUS_G3H to be low (around 1V), which should usually be 12.6V, and noticed a short to ground on this voltage rail. This is one of the main voltages on all MacBooks, supplying a lot of components, and branching off into different voltages for the CPU, backlight, etc.
When there is a short to ground on a voltage line, the first step is to inject a small amount of voltage on this line. A component on the board will be shorting PPBUS_G3H, and when injecting voltage, this component will start to get hot since it will be sending the injected voltage directly to ground. Whenever we have 820-3435, 820-3437, 820-00164 or 820-00165 models with a short on PPBUS_G3H, we check the tantalum capacitors first, when injecting voltage. It is very common for one of these to crack due to a drop, bad battery or just a random failure, which will short the rail to ground.
Surely enough, one of the tantalum capacitors to the right of the CPU was getting hot, and on closer inspection we could see a small crack in this capacitor. We replaced this capacitor, and F7140 (a fuse on the PPBUS_G3H line, which usually blows with this issue, due to the short that was on this line) and the customer's MacBook Air was now booting fine.
Upon fully testing, we did notice the customer's battery was showing a 'Replace Now' warning, and the device was only working on charge; replacing the battery resolved the issue. It's common for the battery to fail with this issue too, and on this occasion, the issue with the logic board was likely caused by the battery failing.
We successfully fixed this 820-00165 which was showing a charging light, but wasn't booting, and the customer was happy they did not have to purchase a new model, and retained their data!
If your MacBook Air A1466 is showing a charging light, but not booting, we can fix this for you. Feel free to book it for our free diagnostic service and we can find out what is causing the issue.
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