heater module question

To begin with,,, my heater , a/c stopped blowing,,,,, we checked the voltage ,,,, was fine,,,, fuse was fine,,,, replaced heater module,,,, worked great. After a 30 minute drive the heater started blowing out at a very high speed,,, could not not turn it down or off using the controls,,,, shut off the car,,, still blowing,,,, any suggestions of what is wrong and how to fix it.... thank you