Chosen Solution
Fans start then stop for not even 1 second, repeatingly, when powered by cable, no pushing of power button needed. when just battery, power button does nothing. tryed shift+control +alt+power button, fans stop, then on release the led goes orange to green and fans start repeating the cycle again and again.
At this point it really sounds like your battery is bad. Lets see if we can by pass the battery. Follow this guide to step 4 MacBook Pro 15" Retina Display Mid 2012 Battery Replacement. Carefully sit the system on its side and press the power button, holding it for a good 15 secs to fully discharge the logic board. Now plug in the MagSafe charger alone, the system should spontaneous start up, did it? If not disconnect the MagSafe charger and reconnect the battery, then plug in the MagSafe charger, you’ll likely need to leave the system under charge for a good four hours before you can test things again.
