Parking break not working

In my 1998 chrysler town and country the parking break pedal wont stay put. When I push it down the lihgt from the break comes on but as soon as I take off the foot it comes back up, I don;t think is the cables because the presure is the same as ii was before every time I parked the car. The pedal just wont stay put. Tha car has 116000 miles on it. Thank you.