Air Conditioning - Air handler blowing, but little air comes out

Used the Central A/C for the first time today. This problem was occuring at the very end of last year but I didn't do anything about it.

I have:
Condender outside
Air Handler in the attic
Completely separate baseboard heating system.

But after about three hours
Condenser is returning cold refrigerant
Air Handler is on
But about 10-20% of the normal air flow is coming out of the vents.
Small amounts of air are leaking out of the normal areas (where pipes go in, corners of the air handler etc..)
If i hold a piece of newspaper to the return vent in the ceiling it does stick, but definately much less than normal.

So if any of you good people have any suggestions, I'd really appreciate it.

Thanks in advance

Have you checked the filter to see if it clean? Also could be a run capacitor on the air handler has gone bad reducing rpms on motor.

Sounds like a dirty filter or the evap coil in the air handler is dirty or frozen. Make sure the sure filter is clean, than turn off the circuit breaker to the a/c open the coil door & see if the coil is dirty or frozen. Shine a flash light across the coil fins to see if the light shines through the other side of the coil to help see if it is dirty, if it is brush the coil off going with the grain of the fins you can use a wet vac to suck some of the dirt out & home depot & lowes sells coil cleaner in their air filter section. Also while your up in the attic check to see if there is an air leak in the suppy & return ducts attached to the air handler.

It's definately not the filter, I've run it with the intake grille open and filter removed.

It seems to quickly correct itself if I run the air handler with the AC condeser off.

Thanks to your suggestions from earlier posts it seems that the the problems occuring where the air gets cooled.

Is this an easy area to access? and if the condensation drain is clogged, is this easy to free up?

Thanks again

If the air flow is good when the air handler is on & the condenser is off your coil is freezing up either from a freon leak or the coil being dirty. Accessing the coil is not hard unless the air handler is installed awkwardly in your attic. I don't know how it is set up in your attic. Just turn off the breaker go to the air handler & remove the access door. Check & see if the coil is dirty if it is try to clean it, if not call a mechanic to check for a freon leak or to clean your coil for you. Your condensation line would not cause your coil air flow to be reduced.