820-00165 Fan at full speed right at the start

[No-Clean]

Board came in not turning on, had plenty of corrosion from ocean breeze, after a good UC board now turns on and boot fine, but board now has fans running at full speed as soon as power is connected to board, this is with board alone on desk with good IO board and flex.

HWMonitor does not show any problems.

 

[2informaticos]

Missing trackpad will cause this.
SMC is searching for TP thermal sensors...

 

[No-Clean]

With new TP and flex connected same problem, the weird thing is that the fan ramps up to max right away no matter what, I remember that in other cases with a good board the fan ramps up slowly.

R4850-53 ARE OK
Newly installed U4810
1 = 3.3
2 = 0
3 = 0
4 = 0
5 = 3.3
6 = 0
7 = 0
8 = 3.3

 

[2informaticos]

Inside macOS, SPI mode is enabled for TP, so pins 5, 6, & 3 MUST all be high.
U4810 is AND logic gate and pin 3 has incorrect voltage reported; change it.
Be sure to have good solders and traces.

 

[No-Clean]

New U4810 Pin 3 and 6 are still 0V with or without TP connected, this is now 3 U4810 important to note that area around U4810 is clean

R4850-53 and R1630 ARE OK
Newly installed U4810
1 = 3.3
2 = 3.3
3 = 0
4 = 0
5 = 3.3
6 = 0
7 = 3.3
8 = 3.3

Sorry for posting wrong info at first.

 

[2informaticos]

Check Q4800/60 and adjacent resistors.

 

[No-Clean]

Looked clean, but replaced them regardless and still same thing.

 

[No-Clean]

All related resistors are OK

 

[2informaticos]

Possibly corrosion under TP connector.
Also reball SMC, as usual for liquid damaged boards.

 

[No-Clean]

Reballed SMC and removed TP connector same problem.

I mentioned this before but I will mention it again, normal behavior with the same exact board in working order is that the fan starts slow and as it notices that the TP is missing or damaged the fan ramps up to max speed, this board here as soon as I connect the power cable to it the fan goes to max right away, I hope that helps with solving the problem.

 

[2informaticos]

Fan spining to max from moment zero is normal starting in SMC bypass mode.
But the board shouldn't start in such mode by itself.

Check Q6060 and its adjacent resistors and traces.
You should change SMC, as it controls the fan.