i have a 92 civic dx hatchback and i just bought a gauge cluster for it with the rpm in it. i was wondering what wire do i have to hook up for the rpm's to work

 

There should be a plug that is just chillin back there not plugged into the current guage cluster. Just plug that into the matching plug and it should work like a charm. (at least i think that's all that needs to be done)..

 

take the old one out, put the new one in. Should use the same exact clips. tach should work with zero modification, assuming it is from the same type of car.