Lights For Rally Gauge Cluster Not Working On a 70 RR

[soundhd]

Was installing a set of aftermarket gauges (3 gauge Auto meter set under the dash). In the process I discovered that the Rally Dash back lighting is not working. (car was purchased late last year and have not driven the car in the dark yet......) When I turn up the dash lighting dimmer wheel to high the dash dome light works (it is a convertible so does not have a ceiling dome light) so I assume the dimmer wheel is working correctly.
So before I pull the rally dash out thought I would ask what I should be looking for that might cause the problem. I looked at the instrument panel wiring diagram and it shows what looks like a multipin connector that feeds all the lighting in the rally dash.......the turn signals and the high beam headlight indicators work ok.......

 

[1970GTX]

I had the same problem. In the end I replaced the dimmer switch. You can try cleaning the contacts with a light emery cloth and electrical contact cleaner.