Heat Not Working But Blowing Cold Air.

My CWH18B seems to be hung up on cool. Going to heat it still blows cold air. It does seem though that for the first few seconds you can notice the "smell" you get like it tries when the heat comes on but then goes away. The temp setting seems to work as it will cut off if you set the heat temp below the ambient but blows cold if running above. I have tried pretty well cycling it through all combinations of settings but to no avail. Our outside temps have been 28-35 at night and 50-60 in the daytime. The filter has been cleaned well and there has been no apparant external coil icing. Unfortunately it is only a few weeks out of the first year warranty, just my luck. Any suggestions appreciated. Thanks..