When you push the button nothing happens.The light has been on for some time now, even in the winter. I get plenty of heat for the winter, and the A/C works as well. What but be causing this? What should I be checking for?

 

Spilled soft drink?

Mine doesn't work so good after I spilled a malt I had sitting on the dash. If I wasn't so lazy I would pull it, rinse, and lubricate.

 

I would take apart the switch and see if it is still doing what it should.
Start there