[Fixed] Ryobi P737 Air Compressor Rattles and Low Airflow

In general, a Ryobi P737 battery-powered air compressor will rattle due to the cooling fan inside disintegrating. You can remove the screws and split the unit in half to shake out the pieces. There are no replacement fan parts sold to the best of my knowledge, and it would be pointless anyway considering these tools are only priced at about $20. Just don't overwork it at any one time so that it won't overheat.
I've found that these units will lose airflow or compression when there is a lubrication issue. Once the unit is split open, remove the e-clips (2) from the gears and slide out the piston for the pump. Clean it out with q-tips and denatured alcohol and lube the piston rings with general purpose grease. Do not get any on the face of the piston.