2014 Honda CRV. The problem is after 20 min. of air flow it stops flowing, but the fan is still working and I still have heat and AC but no air flow out the vents

Sounds llike vaccum problem with the heater 'doors' which switch directon of air flow.

Sounds to me that you might have a leak in the line. Those heaters are all Vacume actuated.

It could be that it took that long for the thermostat to open up. You could try using a longer hose to make sure it flows, but I would want to know if the radiator fan is working too. It does not need the heater itself to cool the engine.

It sounds like your AC unit could be overheating or even damaged.

AC units have a sensor that will turn them off automatically to prevent damage from overheating. If there is an insufficient amount of air flow, the unit will heat up, and then eventually turn off.

When the car is moving, more air is forced over the unit, likely keeping it cool enough to run, however, when the car come to a stop, it loses that air flow, and quickly heats up. Thus, the AC would work while the vehicle is in motion, and overheat and stop when the car is stopped and idling.

However, the AC unit could be completely blown. The cold air while moving could be just a case of air being forced into the car. Think of a house fan, the fast the wind blows on you, the cooler it gets.... Thus, it could be an illusion that the AC is working when car is in motion, when it really isn't.

Hope this helps.

The heat stops flowing this means the air stops blowing. i would say this is one of two things if its the air that stops blowing, this would be a bad blowermotor or the blowermotor resistor, the most common problem i would say is the resisitor, good luck, hope this is helpful.

Most vehicles are vacuum actuated heat and A/C under dash and the blend door on your is staying closed and covering the heater core so no heat can enter. The blend door vacuum line is most likely crimped closed or disconnected. Look on top of the heater box for said actuator and the door hinge to check it. You may be able to see it even.

SOUNDS LIKE YOUR THERMOSTAT IS STICKING,REPLACE THERMOSTAT FIRST OVERHEATING WILL DAMAGE ENGINE.IF THAT DOSEN'T WORK HAVE WATER PUMP CHECKED.FANS WON'T TURN ON IF HEAT FROM ENGINE IS NOT FLOWING INTO RAD BECAUSE THEROMOSTAT STUCK CLOSED,OR WATER PUMP FAILING

did you change the cabin air filter

Could be the flap that directs the air flow. Are you getting air flow to all vents? The flap is inside the venting and controlled by a vacuum operated actuator.

Check that your Radiator fan is operating. The reason that it heats up when stopped is that there is no air flow thru the radiator. When the car is moving there is air flowing thru the radiator (the car is basically cutting thru the air).