Brightness doesn't reduce on battery on Xubuntu 14.04LTS

[jbrawn]

I am sorry if this has been asked before, but I am having this weird issue with Xubuntu 14.04LTS. Everything runs fines except when I switch to battery power on my HP 2000-2b19wm laptop, I have tried using xbacklight and that doesn't work and xrandr doesn't seem to adjust the brightness just the colors. I really want to use Xubuntu on my laptop but this bug is driving me insane. I have tried adding parameters to my grub file. The Fn keys work perfectly just the screen doesn't reduce it's brightness to half when I unplug my laptop from the wall charger.

[kurt18947]

Sorry if I'm stating the obvious here but what does xfce4-power-manager (or whatever is installed) say? I don't have an Xubuntu install with me so can't give detailed help.