A/c-heater fan and face vent issue

Hi guys I have a 2014 peterbilt 579. A few days ago I turned on the truck in the morning and turned the heat on in the truck and put the climate controls setting to face vent. When I got into the front of the truck I noticed that there was no heat or anything blowing out the face vents. BUT it was blowing out the defrost and floor vents. I thought it was the climate control switch, because the fan worked, a/c and heat worked great at the time. But after $400 for a new climate control “cluster/buttons” the next day the fan started turning off and on. So I’m stumped. I don’t want to start tearing everything apart before getting a better direction. Maybe it’s the blend door actuator, or fan resistors? Or both? It seems like it’s something so simple and I’m missing it. Thanks for your help and if I get any new information I’ll post it