door mirror switches

[CliveRothwell]

XJ6 SERIES 3 Mirror switches. This item does not work. It's been stripped and cleaned, every wire has continuity, all surfaces that should be bright are bright. Put it together to be bench tested on know good mirror and it will not work. Anybody got any ideas as to what is wrong please? Or know which part wears out or builds up resistance or something. Also, which colour wire actually feeds power - I am looking at the wires behind the trim panel next to the accelerator pedal. I assumed black.
(Or has got a known good switch to sell me please?) I have 6 switches and only 1 works!! As I cannot find which is the power lead, the good switch and mirror on the bench test does not work on the car............
Thanks again,
Clive.

[mike020150]

The Haynes Ser 3 wiring diagrams appear to show black wires as earth and red as power from fuses 17 and 14, dependent upon which side mirror you are working on. Mike.

[CliveRothwell]

Thanks Mike!