Reply to "No Back up lights"

Well, the mystery continues ………………….
Tonight I tried the following. With the ignition on, lights on, car in reverse the test light indicates power on both sides of the switch. I found a plastic connector with two black wires (mid rear) pulled out of the connector . Repaired and re tested , but I think this is for the AC condenser fan motor. Next I found another set of two black wires factory spliced together attached to nothing. I thought for sure this must be the ground needed for the back up lights. Nope still nothing. Next I re installed the original left tail light assembly . Still nothing. I tried my test light on the two white wires as they go into the connector. I have power on one but not the other. This is really becoming one of those me against Tony challenges. Probably does not matter much I have been driving around for 12 years apparently with no back up lights. I have brake , tail and turn lights which are the critical ones. Again thanks to all for the suggestions.