autometer oil gauge
 

I just installed an autometer oil pressure guage with a sending unit and it seems like it is not working properly. It shows 25 Psi at idle but when you give it gas, instead of going up, it go's down and sometimes doesn't work at all. could it be the sending unit, or the way I installed it? I really don't think there is anything wrong with the pump but I could be wrong. How can I be sure?
Alex