Doggie Door Training

Question
Hello.  My dog is a 1 1/2 yr. Labradoodle/Springer Spaniel.  Currently trying to train him to use a dog door located in a detached garage that leads out to his dog run.  He has no problem heading outside, but I can't get him to come inside through it.  He rather stay outside all day in the cold, but his food, water and warmth are inside.  I've tried repetitive in and out training with treats, but he only comes in if I'm standing right there with a treat.  He does spend his nights in the house with us, so maybe he doesn't like being out in the garage during the day?  Please help!  Thanks.

Answer
Does the door swing differently on the way out than on the way in? Some dogs don't like the doors that have two pieces that swing on the way in or vice-versa. Is the door swinging smoothly? That might affect the perception too.

Here's a link to training for dog door use that may be helpful.
http://www.radiofence.com/dog-doors/dog-door-training.htm
http://www.outlawchinooks.com/
http://RileyTrainingCenter.blogspot.com

Good Luck!