Water spill = Slow laptop, Kernel_Task 320%, Fan loud. Why?
After days of research and homework, I finally decided that asking my own question might be the way to get the best answer to my problem.
I own a Mid 2012 MacBook Air i7, 8gb memory and 256 SSD.
Two years ago I went for an offroad trip, the car sank in the river, the Air was inside the Car. Wet.
Back home I opened the Air, cleaned as much as I could with isopropyl, let it dry few days and tried to boot. It didn't.
I replaced the battery and I could finally plug it to A/C and press ON. But then the fan would progressively reach its max speed and when I was at the step of entering my password it would die. Everytime.
What did I do? I bought a second-hand Pro. Been using it for the last two years and no problem. So three days ago I decided to sell the water spilled Air online to make a few bucks.
But my curiosity was too strong, so I plugged it to A/C and press ON. It booted and this time it did not die!
So I did some research. I went into Activity Monitor and saw: Kernel_Task 320% and CPU system usage at 98% leaving barely 2% for the user.
Then I checked IStat Pro, the fan speed is at 6500rpm but the CPU temperature is barely over 32C/90F and the bottom case doesn't feel warm at all when touching it.
Memory usage seems fine.
I tried to boot in Safe Mode but it was even slower. 20min to open Activity Monitor so I went back to normal mode.
I launched AHT and it gave me:
4SNS/1/C0000008: Th1H - - 124
I understood that T means Temperature and h means Heatsink.
But will replacing the heatsink and thermal paste really fix my Air? Is there temperature sensor within the heatsink that gives false information to the CPU forcing it to run the fan at max speed and be so aggressive with the kernel_task?
I'm quite happy to be able to boot it today even after two years stored in its box waiting for me to advertise it online. So if I could fix it I would be very happy and I would definitely keep it and get rid of the Pro that I bought as a (long term) replacement.
Any thought and advice on what is the problem or what should be my next step would be very appreciated.
Is this a good question?