2003 Chevy Astro blower/fan not working

Last summer the blower/fan stopped working untill the engine had heated up and then it would turn on.
after it had turned on I could use the a/c or the heat both worked. But when the engine was cold the blower would not turn on at all. Now that it is winter the blower/fan dosent turn on at all. I checked the fuse's and they seem to be fine. So I am not sure what the problem is.