My a/c and heat switch is acting up on my 2003 Pontiac Grand prix?

[lost]

A few months ago I noticed that when I had the heat on settings 1-4 would work but setting 5 would just shut off and not blow air. now when I use the A/C setting 1-4 all blow on setting 1 pretty much. and when I turn it to setting 5 it now works.

Any idea what cold be causing this? how hard is it to fix or $$?

 

[melsg5]

burnt out fan resistor