Both of these are possible, and both are easy to check. First, set the controls to heat. If you turn the fan on and it works, then it is not the blower motor. Replace the fuse for the AC, and check the AC relay (in the box under the hood) and see what happens.
Other things that you should look into if that doesn't solve your issue:
Bad AC switch in the dash.
Intermittent wiring somewhere between the AC switch and the AC control electronics, if any.
In a 2003 there may be a dedicated climate control computer. If so, the problems can get more complicated to diagnose. Just remember: Simple things first, and when things start to get scary... get some help with it.
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