How do I know if the power adapter is ok?
The light on my power adapter isn’t on. Neither red nor green. I just installed a new battery. How do I know the problem is or isn’t the power adapter?
MacBook Pro 17″, macOS 10.13
Try an SMC Reset.
Unplug the charger from the electrical outlet for a minute to reset the internal circuitry on the charger. Also try using another electrical outlet (preferably on another circuit). If you are using the Duckhead adapter on the charger, then this part tends to fail. Examine this part carefully to make sure it moves properly and isn't loose. Also make sure there are no charred or burn marks inside the base of the prongs where it rotates.
Here is an Apple article on troubleshooting charging issues:
https://support.apple.com/en-us/HT203207
Try disconnecting the battery to see if the Magsafe LED lights. If not, repeat the earlier suggestions. The quality of third party Lithium-ion batteries is extremely poor. You also don't mention which model Mac you have. If this is a Retina model, then maybe the laptop was damaged when removing the battery.