Dodge Repair: low volume cab air, corn kernal, dodge 2500

Question
We have a 1998 Dodge 2500 4WD with the 360 5.9 litre engine. This is a farm truck and is used in some dirty conditions, particularly corn "bees wings", which are the little sleeves that the corn kernal sits in on the cob.  There is a very low volume of air coming through any and all vents in the cab. Doesn't matter what we have the heat or air set on.We believe there must be a screen somewhere that that is plugged in the heating cooling system. We have dismantled our way to the heater fan and it is fine. We have not been able to figure out how to dismantle further. We have tried sticking an air compressor hose in but can't get enough force in the right place to blow anything loose.Do you have any suggestions or do we have to break down and pay a mechanic?
 Any help would be appreciated.Thank you.
Donna

Answer
hello donna
the only thing else you can try is pulling the tubes off under the dash and see if they are pluged it no then it is a job for a mech. thire is a screen in the upeer dash dash would have to be removed to do this is a big job . good luck to u hun and u have a pretty name pete