The first clue is that it weighs three pounds. The second is a loud CLACK when energized. Low coil amperage, then a detectable jolt then the coil is de-energized. Regular can solenoids that look like a metalized Ford starter solenoid do not have the room inside. They increase amperage for more load capacity but that does nothing for a fast breakaway to minimize arcing and contact destruction.
For some reason :) I cannot find a bad Trombetta solenoid to autopsy. I jump through hoops to minimize failed components as one failure can total ten times the amount of a replacement.
