Central air. At start up the air appears to be functioning well. As the day progresses the air flow from the vents weaken ,unit continues to run unable to cool to set temp.

Is the blower motor slowjng down? Do you have a ampprobe? And can check how many amps the motor is pulling? Coppare to furnace tag to see how many amps it should be pulling,, also possible the capicitor is going bad,, how clean is the filter?

Air filter clean. There is a continues red led light on in the circuit board

Continues red light normally means all is working,, but it doesn`t /can`t monitor everything

Probably freezing up

What might be causing that?

Low on freon