My gas dryer is an Amana Model #LG8209W2. We clean the lint screen before each use. I took apart the vent hose and cleaned it (very little dust came out). There seems to be a very strong air flow exhausting out the house vent. I noticed when I first turn it on it does get hot but then it turns to cold air. After sitting overnight I tried it again and it started with hot air at first and now is blowing cold air only. What's next to test and isolate the problem?