I just installed the autometer pedestal mount tach#5899. I used the same wiring that my prev tach used, but now I'm not getting power at the tach. The old tach worked. The gauge light works, but when I turn the key, the light goes out. The car has been sitting for awhile(winter). Does this tach need a full 12 volts for it to operate. The battery was at 10-11 volts when I checked and the old tach worked fine. All other gauges work, just the tach is giving me problems.