Is the clog from the factory, or does it develop over time? If I just blow it back in, will it just clog again?
It develops over time especially during fall season, I think it must be the trees from my work parking lot and all the dried leaves and crap that gets into the vents at the windshield base.
It's a very common problem with the CX-9, if you search this forum, you'll see at least 5 different threads on the same subject.
It happens to me every 9 months or so, I've tried both methods and still gets clogged after 9 months. As long as it's not every other day, I'm ok with doing it every 9 months, just gotta live with it.
To get to the evaporator core, it is not an easy job and it is quite expensive $$$$$, so most members just try the compressed air spray can or vacuum method first.
If it gets clogged every other two days after draining out the water, then the last alternative is to start taking things apart to get to the stubborn clog.
If you're still under warranty, dealer will fix for free, but I bet they will use the compressed air method took less than a minute to fix, that's what they did the first time I actually saw what they did and a whole gallon of water came pouring out, second time they wanted to charge $75 out of warranty, I said forget it, I can do it myself.
Obviously, 9 month maintenance AC draining is not what most owners expect to do, but that's nothing compared to the transfer case gear oil maintenance on the CX-9 AWD, if you have an AWD, you should check the thread for transfer case gear oil maintenance on AWD 2007-2015 CX9's in the how to section of this forum.