Have some Lights, but not others, Help!

Ok, we took out cluster, found that the metal backing has a constant 8v and the lights came on and the fuel gauge worked with the key on. As soon as we put cluster back in car, the 8v grounds out and lights go out. Is this normal as we might be missing some insulation as it attached to car? Also I think the reason its 8v and not 12v is because of the step down capacitor. We thought we had a wire switched in the connector, but there is only one lead that has voltage and the rest are ground. So polarity reversed? So it might be as backwards, but all light work now with cluster hooked up and out of car. Wow.