Sometimes when I have the heat on high the heater starts to make a purring sound, if i turn it on low it will either quit or get quiter it doesnt do it all the time but its just strange and i dont want my heat to quit working even though ive been gettin eat up by mosquitos in 70 deg weather in the middle of winter its still cold in the mornings.
What causes this? is it a belt getting worn out? or do i have gerbils living in my vents?

 

Yes, It's a family of Gerbils living in there... Don't make us call PETA (people eating tasty animals) It takes to many of them for a decent meal...

You are most likely experiencing the signs of a failing blower motor. Mine made it from Gerbil mode to a growl before it died. Growl mode caused my resister to go out as well... Just something to think about.