I have tried to call local pellet stove stores for help and they wont help me., the auger on my 1991 whitfield renissance keeps getting stuck. even with no pelletts in the hopper. i have replaced the motor and pulld out the auger. it is clean exceot for some balckening around the top. dont know what else to do . the motor is working. and the auger will turn but get stuck before it does a complete rotation and not always in the same spots. any ideas