dash board electrical

Did you have any kind of sparks while you were tightening the battery clamp?? Did you take the clamp off and clean it before tightening it?? Is everything else working?? My guess is that you had a corroded terminal and when you tightened it you lost connection. To do it properly you need to remove the cables from the battery and clean the cable end and the battery post. The battery terminals should be shinny and clean for good connection. You can also put some battery terminal conditioner spray on it once you get it all cleaned up.