I had old kpl, and when the lights were on, there used to be dim backlight to show the names/buttons of the pad, and when turned on, button used to get brighter to indicate its on. I changed to 2334 and its totally dark / off if the lights are off. hard to tell in dark if there is a KPL and the switches. was this on purpose? anyway to turn on dim backlight ? is my KPL defective? 

I have not checked the newest versions, but all mine have the ability to configure backlighting. I would first check on the admin panel. Choose the device in question. Along the bottom of the main window should be options or settings or something. In there I expect to find backlight level settings. Adjust those to your liking.

 

If not, check the keypad user manual for method to make those adjustments.

In the ISY at the bottom of the screen for the Keypad you find an option for adjusting the KPL led backlight. You can set the brightness for both the on and off levels.