How do I clear an ac drain clog

it is close to the center of the firewall,you will be able to reach it from underneath, from the driver's side of the vehicle. It is very difficult to see even from underneath the vehicle. It would be easier to get to it, if you had the car on a rack or over a pit. The catalytic converter is right there, so the engine should be cold to prevent burns. There is also a sub-frame right forward of the drain, that makes it hard to get to and even very difficult to locate visually. crawl under the vehicle from the passenger side and looking across, along the lower rear edge of the firewall it will be there. use a short piece (about 8 inches long) of thin wire with a tiny loop on the forward end, to stick up the hose to loosen the clog. a quart or more of water may come out, push the little piece of wire up inside the drain tube in and out a few times.also change your cabin air filter.