Worked for me. I don't think the gauges care where they get the ground from so long as they get one. If your problem has it's source in an existing faulty ground connection, the new wire will fix it.

The variable resistance that Frank refers to provides the indicator values (needle pointing position). A fixed ground is still needed as a reference.

Use a clip lead to check it out if you wish before you do any wiring.

BTW, I have removed my cluster probably six or eight times by now and have never disconnected my battery when doing so. Maybe I am just lucky but I don't think there is anything back there that can be shorted while the key is off.