I have a Mid 2012 11" MacBook Air that won't charge or boot. I've tested the charger with multiple other MacBook Airs, and the charger works fine. I have researched this and have done everything from attempting a PRAM reset, a SMC reset, to even sitting on the charger to heat it up. Nothing works, but I don't know if you can reset the PRAM or SMC when there is no power. One thing I have noticed is that if I plug the charger in to a working MacBook, let the light turn orange, and then unplug the MagSafe and plug it into the broken MacBook, the light will turn orange. It doesn't charge it, however, and will only do that if I plug it in within seconds of unplugging the MagSafe from the working MacBook. Does anyone have any suggestions?
A similar thing happened to my MacBook Pro - from around the same era.
The only other thing I would suggest is trying a few different wall power outlets and making sure those outlets are working (like with a lamp).
Other than that the unfortunate diagnosis is that your MacBook will most likely have a dead logic board. On the Airs, I am pretty sure most things are directly integrated to the logic board:, RAM, CPU. But the SSD is removable and you could take it out and put in into another Mac to get your data from it, if need be.
Your charger is not the issue as evidenced by your testing it on other MacBook Airs
I've tested the charger with multiple other MacBook Airs, and the charger works fine.
You have a problem with either your logic board and/or your DC Power I/O Board. You need to take it in for service.