Chosen Solution
I received this system from a customer. It seems that it’s OK (except its really slow). I tried SMC to check if it would charge when its on, but doesn’t work but, when its off the mac, the LED goes Amber right now, it’s been like 10 minutes since I shut it down, I’m gonna wait if it goes beyond the 2% What software recommend to check the health of the battery, according to the system report it says “its fine” Update (07/14/2018) So I replaced the battery with another MacBook that I have and I notice it’s not charging either, it says that the battery is not charging, is depending on the charger? Also I tried with the other charger and it says the same message, and I realized that the other system is working fine with this battery, I can’t say it needs a battery if I can’t charge the battery. Update while writing, I downloaded TG Pro and the systems readings are OK. The only thing that I have to check is the MagSafe port if I have to replace it.
This is probably the best App for Mac: https://www.coconut-flavour.com/coconutb…
If the system is really slow it’s likely in SafeMode as one of the thermal sensors is telling SMC the system is overheating or the sensor is missing. The easiest way here to check is to run this app: TG Pro paste a screenshot of the main window (You’ll likely need to stretch the window a bit so all the sensors show up) here for us to see Adding images to an existing question Update (07/15/2018) It does sound like your DC-In Board needs to be checked. Review this Apple T/N to make sure your using the correct charger and as a reference on what the MagSafe connections look like: Apple Portables: Troubleshooting MagSafe adapters. Here’s the IFIXIT guide to replace the DC-In Board: MacBook Pro 13" Unibody Mid 2012 MagSafe DC-In Board Replacement Its also possible the charging logic on the main board needs repairs. Did you get CoconutBattery working? That might offer a clue here.
