Yamaha gauges , one gauge works other gauge blank ?

[No more boats]

Yamaha is new territory for me ,
Another question for group
GAUGES - Yamaha
engine is 2000 , 2 stroke , 250
Think engine is OX 66 , cant read serial number ,
RPM gauge works ,
other gauge speed - time - temp - fuel =-blank screen ( engine running )
red lead into gauge , hot , does it turn on automatically when engine is operating
If it has juice would zeros or something indicating its operating ,
How can I test if gauge is working ?
thanks

 

[Jprevat]

Should turn on when operating. All leads are good with no corrosion?