Why is air blowing back through my above ground pool filter system.Swimming pool troubleshooting?

You most likely have a suction side leak. In most cases you will not see water leaking at these places. Sources to look at: low water levels, skimmer weir stuck not allowing water to flow easily to the pump, a broken suction line from the skimmer or main drain, loose pump lid, loose fittings in and out of the pump ( caused by low water levels and pipes getting hot), pin hole in the volute side gasket of the pump and worn our pump seal.

Ken

I agree with everything Ken has said above and just wanted to add something else here. You may also just have a air lock in your pump, on most above ground swimming pool pumps you will have a screw lid on top of the pump. Unscrew that lid slightly and let the air out until you start seeing water coming out. Then re tighten the lid and that may solve your air lock.