Dimmer Switch

Every dimmer switch has a minimum load. In order for a dimmer switch to dim, a certain amount of wattage needs to be available.

For example:

Halogen Downlighters	CFL Downlighters
A room containing 10 X 50W halogen downlighters. The total wattage = 10 X 50W = 500W (plenty of wattage to allow your lights to dim).	If you replace each of these with a 7W CFL downlighter, the total wattage is reduced to 10 X 7W = 70W (way below your 100W minimum load requirement), which is why these lights will not dim.