Go to autometer's website
http://www.autometer.com/tech_instructions.aspx
Re-read your install a few times until you grasp the concept, check your wiring 2x after you have thoroughly read the instructions.Start her up and give it a go.
It could also be depending on the location you placed the sender, if you grounded everything cleanly (no paint on metal ground points)
As far as I remember they (Autometer the company) do not warranty parts damaged due to improper installation, BUT if you bought them from a local speed shop you *might* be able to get them to do an exchange it, and they claim shipping damage on your broken unit(if its broken) and everyone comes out good