2001 Chevy Impala Heater is screwy

Please bear with me because I do not
know all the Car lingo so I'll do my best.
When I first got my car the heater was
really loud when it was on and only number
two through four would work on the dial.
So I had the dial connector on the inside of
the dashboard replaced and  I could use
the heat on one through five on the dial.
After I fixed that sometimes the heat
blower would just shut off and couple
minutes later it would come back on. Well
last week it went off and never came back
on and it smelled like it was burning a
crayon even though there were no crayons
near where the smell was coming from.  So
I had the heater/blower replaced it's a  one  
piece of equipment. It worked for about 48
hours and now the heat will shut off while
I'm driving and if I shut it off it will come
back on. But earlier today it did not come
back on it shut off and I was driving when
it decided to come back on. So I need
some help please if someone can tell me
why my heat goes on and off please it's
driving me crazy. Thank you.