Regarding a 4-light kit on a residential ceiling fan (Hampton Bay). 20 A circuit, nothing else on in circuit (house is vacant). No wall switch; all switching done at fan/light kit (separate pull chains). Fan turns fine. 122 VAC as measured w/ a Fluke meter within light bulb socket.

Have tried multiple bulbs, bulbs won't light. Tried same bulbs in other different fixtures, they worked. Replaced bulb sockets, same voltage present, bulbs still don't work. Tried WD40 & petroleum jelly in different sockets for better conductivity, still don't work.

How can voltage be present w/out lighting a bulb? Confusion reigns!

Check wiring between the fan and the light kit. A faulty connection, one that makes a connection but just barely, could give you voltage but not allow enough amperage to pass to light the bulb.