AC wont work on setting 5

I have a 2002 trailblazer and the air stopped working on the highest setting. It works on all other settings just fine,and the rear air works fine as well. What is likely the problem? Its going to get cold soon and with two little ones I need this fixed.

The blower relay/control is bad, very common, on the blower case under the r/s of the dash behind the glove box.

Thanks I ordered the chevy oem part from www.gmpartsclub.com (http://www.gmpartsclub.com) so hopefully it will be here in a day or two and I can get this fixed before it gets very cold. Thanks for your help