I have a Husky (Campbell Hausfeld) 80 gallon 2 stage compressor and it does not unload when it reaches capacity and when I drain air down it kicks reset switch.
Where is the unloader valve located on the compressor?
For many air compressors, the unloader valve is adjacent to or part of the pressure switch.
It’s can be a lever protruding from the side of pressure switch that toggles the unloader valve open and closed as the switch cycles.
Other pressure switches have the unloader valve internal to the switch. These can be identified as there is an air line inserted into the bottom (typically) of the pressure switch.
Unloader valves can become plugged up, so when you find yours, after dumping pressure and unplugging the compressor, disassemble and clean it and see if that solves the problem. If not, you may need to replace it.
If you add a photo of the pressure switch on your air compressor, that would sure help.