Grand Caravan 2005 brake lights lights when stopping

About a week ago I had to brake hard on the highway. The brake light lit for a couple of seconds. Now about 1/2 the time when I stop the light lights for a couple of seconds. The fluid in the resevior is up to the only line I see which makes it about 1/2 to 1/3 full. I didn't want to add fluid for fear of overfilling. Does this light light when the pads are getting thin? I have 57k miles on the vehicle. I'm supposed to take a trip tomorrow so this problem has me concerned. The brake still feel like they are working fine. They aren't spongy and I notice no difference in my braking power.

I'd appreciate and help I can get.

Thanks!

Rob

The light will light when it see a differance between the front and rear brake pressure. Sounds like you might need pads or shoes.

As your pads and shoes wear, the fluid level will decrease. Low fluid is one thing that will turn on the brake light. 1/2 to 1/3 full sounds too low. Check your drivers manual on how to check the fluid level and add some fluid.

A little back ground info: http://auto.howstuffworks.com/master-brake2.htm