Electrical mystery.....

The power probe is great for trouble shooting. Hooked to a battery, pos and neg, you can use the probe to inject ground or power to test both sides of the circuit. As in the said light socket assy. With bulb in, and powered, you can touch the probe to the outer part of the bulb, and touch the neg button to ground out the probe. Does it light now? if so, bad ground in circuit. Still not work, touch the probe to the power wire of socket, touch the positive button, probe now is hot power wise, light should work. If not, bad connection at bottom of socket to bulb. sometimes the little solder point at base of bulb is worn so does not touch hot wire in socket. It is a great tool, also works on 28 volt systems.