Dell Latitude 5420 wont turn on when charger is connected

[nikolayu]

I have Latitude 5420 that it's working fine on battery but when it's plugged on USB C charger it wont turn on.
Battery is charging fine. Also, if I connect the charger while laptop is on, everything is fine, it will charge.
The same thing if I connect to other USB C port.
Charger is OEM

[mon2]

Remove all power. Meter in resistance scale. Check the resistance across DCin PQ49 mosfet as follows:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. No power during these resistance checks. If the resistance is low, the mosfet may be shorted.

[nikolayu]

There is no DCin. It charges only via USB C

[mon2]

Do you have a link to the schematic for this unit?

Which charger IC is onboard? Post pics of the charger IC. Nearby the charger IC will be the DCin mosfets. They will be used to accept the power adapter voltage (USB Type C for your case) and it will be passed onto the main power rail. You need to review the 2nd DCin mosfet in this power path.