The blower relays sometimes go bad. There are two relays, one for each blower. You can swap the relays to check if one went bad. There are many threads on the forum - search for blower motor relay and something should come up.
The other thing it can be is a bad blower. These sometimes fail if the drain gets clogged and water backs up into the blower. There are aftermarket replacements available for about $50. Make sure the drain is not clogged before replacing.
Here's a link to a thread about this:
I reluctantly sold my 2008 CX-9 to my Pop just 1 year ago.....on the promise that I get first dibs when he goes to sell it! My parents called me yesterday and tell me that the A/C isn't working, so they came by last night to let me look at it. The A/C was actually working fine, but there was...
www.mazdas247.com