Most people find they have to disconnect the AC lines above the climate control box in order to open it enough to be able fully clean all the leaves/dirt out.
I simply removed all the self tapping screws that hold down the top of the evaporator/heater box. Then I removed the heater resistor completely. I pried the top of the box open about and inch and wedged it, holding it open using a block of wood. I also gently moved the fin sensor and its wiring off the side a little bit, being very careful. I was then able to use a small 1" vacuum hose attached to my cheap household DirtDevil vacuum cleaner attachment hose and vac out most of the debris.
Vacuum the box out though the resistor block hole or through the top gap while gently brushing the debis loose with whatever small brush you can get in there and just do the best you can with the space available. I used a custom turbine wheel brush that can be found at auto parts stores, but a small dish scrubber brush, long toothbrush or anything similar with nylon bristles will work. I couldnt get the front of the evaporator 100% clean but I was able to remove 70 - 80% of the leaves and junk that were clogging up my evaporator.
It is certainly not a perfect solution and you won't get all the crap out. But it improved the airflow and worked well enough for me until I finally got fed up and replaced the evaporator core a year later.
Last edited by blackvan; 10-01-2013 at 12:44 AM.