Galaxy Note 9 giving a false positive on over heating.

[HELP290]

I just did a repair on my sisters Note 9. The repair was for water damage which, admittedly may have been my fault. 

 

I followed a guide to try to fix the phone. Good news it works enough to turn on when plugged in. The bad news is that the phone thinks its overheating when it clearly isn't. I cant boot into safe mode since the warning is so quick to show.

 

There haven't been many resources I can point to online to help me with this.

 

Also a battery isn't installed since I don't have a fresh one to use. Thank you for your time.

 

UPDATE: Sorry I have taken a while to update this. As it turns out the issue was with the wireless charging. The wireless charger part has a temperature sensor on it, I didn't have it plugged in which meant the phone couldn't read temperatures.

The phone is fixed now.

Edited May 23, 2022 by HELP290
Found and solved the problem

[da na]

It seems to be a short on the motherboard, or some damaged jumper somewhere. If it was previously water damaged, is there any damage around the main chips, rust on the board, etc around the CPU, RAM and storage?

[trag1c]

I assume the probe that is on whichever IC is overheating is working so would suspect a short as well since high resistance doesn't generate heat. Since a lot of the IC packages are BGA (or even smaller like WLCSP) you might have water that is sitting between the pads underneath the chip. Since these are very short distances between pads it makes it very easy to form a conductor between power and ground. It might not be low enough resistance to burn anything but it could be enough to heat things up.

[HELP290]

35 minutes ago, Mel0nMan said:

It seems to be a short on the motherboard, or some damaged jumper somewhere. If it was previously water damaged, is there any damage around the main chips, rust on the board, etc around the CPU, RAM and storage?

Seems reasonable, what's inconvenient is that the board I'm working with has metal guards over the chips. Which makes it hard to access them.

I tried my best to clean corrosion, and got everything I could see.