sunfire heater fan problem

2001 sunfire: heater fan stopped working EXCEPT, after it stopped working for several days, then one day went out and started car and fan worked just fine! no bearing niose, worked great, then after work, went back out to car and it doesn't work and still doesn't. Tried ALL settings, ect. fuses and relay all seem ok.
Any ideas what the heck is going on?
Thanks