I have had this jumpstart pack for ~15yrs. Still works. Well, until today.

The air compressor is operated by switching GND (held in fingers). This corroded (white blob) at the PCB, and when The Bloom Of My Desert turned the pack off, the wire broke loose. The wire then contacted some random ground inside the device, completing the circuit and running the compressor. There is no other off switch. Turning the main contactor off did diddly and The Guiding Star Of My Night had a ZOMBIE MACHINE!