Chosen Solution
My MacBook Pro A1990 fan began erratically spinning. I reset the SMC to no avail. Fan control will intermittently sense it as spinning, or will report it at 0RPM (which is when it begins spinning faster). I replaced the R fan which was the misbehaving fan, and this behavior remains. All the temperature sensors appear to be operating normal. Hardware test shows PPF003 PPF004 which is what it showed prior to fan replacement as well. I’m at a loss, is there another part besides the logic board that could be responsible?
If the behavior is the same after replacement, I would also look into your keyboard cable. As I’m sure you noted when you did the fan replacement, the fans actually connect to the keyboard’s board, not the logic board. The cable which then connects this board to the logic board carries signals for both the fan and the keyboard. Apple tapes over the connector on the keyboard end, but it’s possible this cable is bad, has come loose, or something to that effect. Otherwise I would make sure the fan connector itself is sound, and the little locking latch is in place. If not those, then it’s very possible it’s a logic board issues.
