Hello,
I have a 1995 Chevy C1500 Silverado. The blower and heater work great when I start driving. After about 20 minutes of driving on high blower speed, the strength of air blowing out reduces drastically and eventually no air is blowing out of the vents. I can still hear that the blower is blowing air, but there is no air coming out of the vent. The Midas repair shop I frequent couldn’t reproduce the issue on their short test drive (of course). They told me to bring it back to them whenever the problem occurs. I haven’t had the opportunity because by the time I get out of work, they are closed and I am freezing to death every morning.