821-2915-B One second fan Spin & Stop loop

[macfix]

Hello everybody

Working on this board wtih fan spin&stop loop. I don't know history but worked some one on it. (not liquid sing or like that)

PPBUS_G3H 12.6V and stable
PPVRTC_G3H 3.3V and stable
PP5V_S5 5V and stable
PP5V_S3 5V then 0V over again
PM_SLP_S5_L is up and down continuos.. but interesting thing is after few minute fan stopped completely and PM_SLP_S5_L , PP5V_S5 5V stable GPU is hot but no CPU Vcore and no ALL_SYS_PWRGD.

 

[smiba]

So its power cycling, check for short to ground on all S3/S0 lines

 

[dukefawks]

Could be anything. Is it an Apple refurb board with no serial number on the RAM slot?