Will a new battery fix my mac air?

Model A1466

4years ago it was spilled coffe on the table the computer was laying on.

I opened and cleand the computer.

It worked ok for 3years, only noticable issue was Screen became dark/dim if connected to charger.

And the battery charged to 100% fast, and drained fast.

For 1year i just left it, and now started it again.

Now the battery says X.

No %.

Tryed taking out the battery and plugging it in again.

(Nothing wrong with charger)

I tryed removing the Battary, and switching on the comuter only with charger plugged in: then the computer powered on, but the screen was verry dimmed - like no backlight. (Original issue)

Does anyone think replacing the battery would help

Or the pcb where the carger is connected on the left-hand side. (I/O board)

Or maby the I/O board cable,?

as that is the only place the 'liquid'-marker has become red.

NB: might there be any connection to the screen damaged ? Cus the screen 'is on' when the Power adapter is on, only the screen will be so dark i cant se whats on it.

If i drag out Power adapter screen lights up straight away.

EDIT:I run the HW test, and it did not find any issues, even wit the battery showing X, and the caharger not showig the green/orange light.

I could start the test with only on battery, and it does look like the Computer is working, although the screen is black/dark.

Since when i unplug it, its has the same window open, and I se the HW test has run for ca 44min...

- i find it strange it dosent find any faults. When Mac is fauly.

Ive don Pram reset and the other reset as well. Battery still says X. And no sign of charging.