MacBook Air 2015, 820 00165 A, keyboard/touchpad works only pre-login (liquid damage)

Hi again and Happy New Year!

The same unit that had a backlight issue. (
Just got the password from the client. on login screen both touchpad and keyboard work perfectly
The moment I log in, they are gone.
I am hoping it is a common issue

Edit: tried safe mode, no keyboard/touchpad even on the login screen :/
Last edited:


Staff member
Is not common fail.
Trackapad communicates with PCH through USB before login into OSX.
Once logged in, communication is done through SPI bus.
Check al R4850-03 resistors and voltages for U4810.
Thank you 2informaticos

R4850 33.4 ohm
R4851 33.6 ohm
R4852 33.3 ohm
R4853 33.3 ohm

The resistors seem fine I guess


1 3.33v
2 3.30v
3 0v
4 gnd
5 3.33v
6 0v
7 3.33v
8 3.33v

Measurements taken with only power and the fan connected


Staff member
You must take voltages for U4810 before and after logged in...
Then compare how react its inputs and outputs.
Thank you!

As I started to look into ways I can check the voltages while running the os, I noticed that the issue is with the flex cable (touchpad to mobo). I had a similar unit - new flex fixed it

Thanks again!