Vents start reducing in air volume after truck is running

[Vinesq]

I have a 2016 Ram 3500. Here lately I have been able to run my A/C for about maybe an hr. or so and then the Volume of Air coming out of the Vents starts
to reduce greatly until finally there is no air coming out. Sounds like its a blowing, but it is not. I have been able to let the Truck set for 30 minutes to an hr. and
after cranking and getting back on the road it will blow good for a while and then reduces again until nothings coming out. I haven't had a chance yet when it
has done this to dig into it yet. Any Suggestions? If the Blower Motor or Resistor is going out and they get hot, will it cause the reduction in volume coming out of the vents? I would appreciate any insight on this matter.
PS. Nothing changes with adjusting fan Speed knob, switching from A/C to Heater or Redirecting Air Flow with knob.
Thanks!!!!!!!!!

[JohnHere]

IMHO, it's nothing electrical. I'd say that it's a classic low-charge condition causing the evaporator to ice up, which in turn blocks airflow.

[Cusser]

IMHO, it's nothing electrical. I'd say that it's a classic low-charge condition causing the evaporator to ice up, which in turn blocks airflow.

Or the air is being directed to the windshield (defrost mode) or under the dash (heat mode) by the flaps/doors in the air flow. There are actuators to control that.

[Vinesq]

Thanks for the help!
I drove the truck today. It lost air flow out of the vents after in 30 minutes or so. Though until then it was good and cold and with good pressure! Got home, looked under the hood and the line is frozen as it comes thru the dash wall. I let the truck idle in my yard for about 30 minutes. I go back out there and the line is not frozen any longer and getting good air flow out of the vents again!

[JohnHere]

I think it's the refrigeration system being low on charge, and that when the airflow stops, you'll find the evaporator clogged with ice as well, although you can't see it. Shutting off the system for a while allows the ice to melt, and then the system cools again--until the next time the evap freezes.

Slight refrigerant leakage over the years might be due to losses from the compressor shaft seal. The remedy is to recover, evacuate, and recharge unless it's an obvious leak someplace else.

[Cusser]

Happened to me in early 1980s in our 1975 Chevy Luv truck: diminished volume of air coming out of the vents after a few hours of driving. Stopped for dinner in Parker AZ, came out and saw a big puddle as ice from the evaporator had melted. That ice had blocked the air flow.

And no electronic flaps or actuators back then...

[Carguychris85]

I do not know if that year Ram has a cabin filter, but I have seen cabin filters so plugged up with debris from never being changed cause the evaporator to freeze up.