Really weird issue

[EnteriiB]

Got a weird one here. Mid 2012 13 inch air. i7 8gb ram. If you turn it on it powers up chimes and then switches off at the Apple logo screen.

However if I hold a key down any key it boots up normally. If I let go of the key it will stay on for 30 secs then turn off.

No water damage. Apple diagnostics say no issues found. Any ideas

Thanks in advance.

 

[Audit13]

This happens with and without the charger connected?

Try disconnecting the battery, connecting the charger, don't touch the machine, and see if the machine boots up by itself.

 

[EnteriiB]

it cannot see the battery in OSX system report which is weird, it boots with the battery unplugged as long as i hold a key. I am leaning towards either the SMC firmware has got corrupted or a logic board issue.

it starts out dark and i have to turn the brightness up within OSX once i am in. so i think that somehow the SMC has lost a lot of info.

whats weird is as long as a key is held down it works perfectly

 

[Audit13]

I recommend disconnecting the battery, connect the charger, and don't touch the machine. The machine should boot up on its own and function, although it will not run at full speed since the battery is not connected.

 

[EnteriiB]

if i am not holding a key it will just shutdown regardless if the battery is plugged in or not. It makes no difference what key is held down as long as one is.

i have been using the fn key boots into OSX and works just fine until i take my finger off the key and then it shuts down. never seen or heard of this before. I repair Macs for a living and this one has me baffled LOL

 

[Audit13]

Try disconnecting the trackpad/keyboard cables from the logic board? Maybe it has something to do with the keyboard since the keyboard signals may travel through the trackpad?

I don't repair Macbooks for a living but I've come across a few with liquid damage that I have managed to troubleshoot.

 

[EnteriiB]

worth a shot, will give it a go

 

[Audit13]

Good luck and report back.

I sympathize with you because these issues can be frustrating and time-consuming to diagnose.

 

[EnteriiB]

will do, i got given it for free as they could not even get it into OSX. with the specs on this i would love to fix it and use it as my daily driver as my Pro is getting a little long in the tooth lol

 

[Audit13]

The best deal I got was for a two 2015 Macbook Airs from Kijiji.

One was pretty beat up and would not power up but it had a 256 GB SSD. Second one had liquid damage to the trackpad and the fan would always spin at full speed (couldn't perform a NVRAM reset because the internal keyboard was not working).

I managed to take parts from both machines to create a single working machine

 

[EnteriiB]

Yep unplugged the keyboard cable and boom no more issues.

 

[Audit13]

That's great news. At least you have narrowed down the cause to a couple of things.

 

[EnteriiB]

if i remove the ribbon cable, battery shows and is charging and it boots no issue. Plug the cable back in it either does the switch off to half the keyboard does not work. ordered a 30 buck replacement

 

[Audit13]

Which parts did you order?

 

[EnteriiB]

whole top case part with keyboard

 

[Audit13]

Wow, that's a great price!

 

[EnteriiB]

ebay

 

[Shirasaki]

I guess somewhere on the keyboard, the circuit is not connected to the power button well. By pressing any key, the machine can be powered on. Again, just my guess cause someone on YouTube posts a video analysing how Apple keyboard works.