DA Problem

There has GOT to be a basic problem here. A 6.5 hp compressor should operate that sander fine, regardless of the size of the tank. 15 seconds? This sounds like either something is freezing and plugging as suggested, or you have a regulator that is failing. You have an inline trap/ filter? Pull it apart see what is inside. Regulator? Bypass it

Try something besides the sander.........a blow gun......or just an open connector nipple. Plug in a quick connect nipple and use it as a blow gun. The thing should flow loud, fast, and hard until the tank starts to exhaust itself and the pump kicks on.

Please detail......or post a photo............of what is inline between the tank and the sander

One person's take on the bullshit ratings of airflow and motor HP

Evaluating True Horsepower and CFM Ratings of Air Compressors