I have had exactly this happen where reversing the wires made it work. No idea why. Glad it works!

-craig

On Jul 26, 2012, at 12:03 PM, Richard A Jones <Jones@Colorado.EDU> wrote:

> Craig:  I had tested continuity through the switch.  That's
> why I was looking further.
> 
> Bill:  I traced back from a tail light--to that black box.
> I put on my glasses and found the connector, yellow with
> one wire in, two wires out, black/blue.
> 
> No continuity there, so I went back under to the switch
> and retested.  Then I reversed the wires on the switch tabs
> and my backup lights work.  Either I didn't do a good enough
> job cleaning up the contacts or there is a wire break that
> I flexed enough to make work again.  Time will tell.
> 
> Richard