My legacy brighton doesn't have a tachometer. So I went to pick and pull and pulled a cluster out from another vehicle with a tachometer. I installed it and everything seemed to go okay until I drove home and had no speedometer. So I pulled my old speedometer out (thinking it was a loose connection in the back) and switched it with my new one. The speedo worked but now the tach did not. I'm wondering what the problem is with the wiring? Do I need to wire the tach through the speedo? Or should I try putting the tach in my old cluster?