House broken dog no more

Question
My 3 year old yellow lab has been house broken since he was 12 weeks old. For the past 4 months he has been urinating in the house. I have a dog door, so he has access to the outside 24/7.  

Answer
That sounds like a leadership challenge.  Neuter him if not already.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm