There's 2 bulk connectors on the dash cluster, 1's kinda in the middle, and one's off to the right ( setting in seat facing cluster ).

It's possible 1) 1 or both have loosened enough to not connect. 2) the voltage reg has fried the gauges or it's not working. They (gauges) come out easily from the front. Take one, get a AA or AAA battery and use it to test your gauge. either post for either (+) or (-). Get some contact cleaner and spray the contacts from the front side (facing you). You can take needle nose pliers and work the connectors around and maybe Q-tip them if you can. I have a couple extra non-tach clusters if you would want or need one.