I have a 2001 dodge ram 1500 and even when I turn the a/c to the off position, it still continues to operate. What could cause this?

I have a 2001 dodge ram 1500 and even when i turn the a/c to the off position, it still continues to operate. what could cause this?
The switch may be shorted internally to the on position.

The A/C control relay contacts may have arced together. Try another relay and see if the problem persists.