MB Air not charging

[JIMAIR]

battery started dropping % charge even when it was plugged in and hit 0%

-I bought a new charger and that didnt work ?
-reset the SMC over and over and nothing
-Bought a battery from IFIXIT and that didn't do it ? (they do say some OSX El Capitan 10.11.x dont like the aftermarket batteries)
-coconut battery says my original OEM battery is "GOOD"

-the light in the charger doesn't come on even with no battery connected
-the MB worked fine at first as long as it was plugged in (starts automatically when plugged in dies immediately when unplugged)
-then it got really slow (safe mode?) i removed the battery and its back to working fine now plugged in
-no liquid damage, i have owned this computer since new

watching fix it videos and reading lots and I cant diagnose this myself. That Rossmann guy talks a lot about a 1 wire circuit and the I/O board in similar situations but i don't have all his fancy diagrams to test voltage at one of those tiny points. its a Mid 2012 macbook air 11"

how do i figure whats the problem without replacing more then i need on an old computer ?

 

[DeltaMac]

You can try replacing the I/O board. That's the part that should fix your issue.
https://www.ifixit.com/Guide/MacBook+Air+11-Inch+Mid+2012+I-O+Board+Replacement/12344

 

[Ruskes]

Resetting SMC can be tricky.
To know for sure if the reset worked, watch the MagSafe light briefly flicker during reset.

--You Mac will run at Half CPU power if not batter is present or working (been slow).
Every battery has that chip build in (one wire) it provides information to the SMC.
That is why they are called SMART battery.

Open About this Mac >Syst Report > Power >Battery
Look at the current (Amperage) consumption with Charger plugged in it should be zero