Interior Fan Malfunction - HELP

I need a little assistance if you will... '05 Chevy Trailblazer... This does not have the electronic controls that were photographed in another post, but the manual knobs instead. My interior fan contoller for the AC and heat no longer works correctly. The air conditioner cools, and the heater heats, but the fan doesn't blow on settings 1, 2 or 3. When you put it on 4, it blows like crazy! Switch it to 5, and it turns off again. I am NOT a mechanic, but am certainly willing to give it a fix! I've enjoyed reading these forums for years, and have pulled lots of advice from the posts, but this is the first time I've ever written one myself...

Any ideas? Thanks!

Welcome to AF. Easy one and common, the resistor relay pak is bad, under the r/s of the dash on the blower case just up and to lt of the glove box.