A1398 Pulsing on off fans no boot

[BCConnection]

A1398 Macbook Pro

Computer originally came in with bad track pad. Replaced the track pad and sent it back out. 4 months later it returned today.

Computer has Green light that changes to orange
Battery plugged in I get fan spin no boot. Fans pulse on off on off constantly

SMC reset no change
PRAM reset no change

Unplug battery with charger plugged in green light changes to orange wont boot and no fan spin

SMC bypass fan spins on high as it should and computer boots and works.

No liquid damage and no signs of any other problem. I assume its an SMC issue but not sure where to start

 

[dukefawks]

Yes there is liquid damage that is why the trackpad died and now the board. Probably corroded trace or resistor in the ISL6259 sense circuit.
Also need board number if you want specific advice.

 

[BCConnection]

820-3332-A

If there is liquid damage Im not seeing it

 

[dukefawks]

Measure resistance between pins 17/18 and 27/28 of U7000.

 

[BCConnection]

17/18 3.8 ohm
27/28 22 ohm

 

[dukefawks]

That seems ok. What is PPBUS voltage? Are you using a known REAL 85W charger?

 

[BCConnection]

Yes getting a third now to test again.

PPBUS 12.45V

 

[BCConnection]

Must have been the charger. Thank you Duke. Time to order new charger for them and me :/

 

[dukefawks]

Get an ORIGINAL one from APPLE, no after market junk! Only charger on the work bench should be an 85W.