1999 Jeep TJ Air and heater control unit

I been having a problem with my air conditioner and heater control unit since I have purchased my 99 jeep wrangler sport. The control unit blower will stop working and will work occasionally if you hit the control unit a few times or hit a hard bump in the road. This will happen off and on until eventually it stops working all together. The dealership replaced the part once under warrant. I have also replaced the part three times and again the unit will work for a few months before the same issue happens. One unit had the rear of the plastic case warped from what I believe excessive heat. I also replaced the module under the passenger side dash thinking this may be the problem and it did not repair the problem. The control unit will still change positions or switch from hot or cold, but the only air movement That I get is when the vehicle is moving I will get a slight breeze coming out of the duct work.