Gauge Cluster Power Problems

[SeVa-S13]

Well I have an R32 Skyline cluster in my 89 240 and it's acting quite odd.I connected the yellow/red wire (Tach signal) and it's getting a signal, but it's very weak. The tach does not rise with the engine's revs and when I open the door or anythign else draws power from the dash/gauge harness, the tach lowers. (Like a bell or my auto seatbelt engaging. It's really weird.)I have no other dash compenent reassmbled so there are alot of open plugs right around the steering wheel/dash area. Dunno if that helps.

Also, I was told to ground the gauge cluster again...which wire is that? I didn't have to cut a ground wire when I took it out so I can't see why I would have to make a ghetto ground now but whatever, aslong as it works. But what do I ground exactly?

Please help.