Screen light with power cord

[HP247]

I have an HP laptop, which has just returned from service. It was having problems charging the battery and they put in a new motherboard.

Now, it is charging fine but the minute I pull the power cord out and the laptop is on battery power, the screen goes darker. Not dark enough for me to not see anything, just simply darker.
If I plug the power cord back in, the screen goes brighter straight away.

Any idea why it's doing that?

[SpywareDr]

Probably supposed to work that way, (i.e., turn off the backlight when running on battery to conserve power). There may be a setting somewhere to override it though. What model HP is it?

[HP247]

Probably supposed to work that way, (i.e., turn off the backlight when running on battery to conserve power). There may be a setting somewhere to override it though. What model HP is it?

The thing, it never used to do that before (as in, the light going dim when it's running on battery power).
I don't like it, an I wanna get rid of it.

I'm not sure of the model, it's a 'pavilion' if that helps.

I tried changing the power schemes, but it didn't help.

[SpywareDr]