820-00165 cpu and proximity memory sensor at 129°

Hi, I receive a water damage board.
After cleaning the board and changing the trackpad flex. Fan spins at full speed.

I install hwmonitor and CPU 1, CPU 2 and memory proximity shows 129°.

U5800 area looks fine, no water near it. Traces to Q5810 and Q5860 have continuity. With webcam unplug same problem.

If I keep hwmonitor open, sometimes shows T° correctly for a couple of seconds, but even if sensor shows the right temperature fan keeps at full speed.

SMC area also don´t have water damage near.

Please tell me if I'm missing some test or if I should change U5800 or SMC?
I test board in another case, with known good LIO flex/board and trackpad flex/board. Same problem.
R5360 and R5361 are good, 2k resistance each.

I also test a known good board with the LIO flex/board and trackpad flex/board of the water damaged board and all works fine, fan at normal speed.

So problem is in the board.
Water damage was in the trackpad conector and in the BL caps and diode. I didn't find other areas with visible damaged.

Can U5800 get damaged, because of the trackpad conector corrosion?


Staff member
SMC, PCH and U5620 are on the same bus with U5800; ALS has been discarded.
You should change U5800 first.
Hi again, after the change of U5800, the CPU 1, CPU 2 and Memory Proximity show normal value.
Fan are still at full speed.
Also PECI SA at moments show 0°, but most of the time shows some value, even showing a value fan at full speed.

Trying to lower the speed with fan control, does nothing. Not sure if you still can do that in Mojave.

I also remove the silicone from SMC and apply heat (240 C°) with flux to the SMC. And did another ultrasonic cleaning, to see if I was lucky.

Is that PECI sensor related with U5800, maybe I need to change that again?



Staff member
PCH is connected in the same bus with U5800.

Manualy tried to set the fan to follow some particular temp sensor, in Macs Fan Control?
With other fan is also at full speed.

FAN_RT_PWM = 4.58V
SMC_FAN_0_TACH = 1.65V
SMC_FAN_0_CTL = 3.28V
PP3V3_S0_FAN = 3.32V

Resistor values are good.