My tach reads double. It used to read correct. It is a 85 Trans Am 305. It has sat for about a year and i fired it up the other day and now the tach reads double. Does anyone know how to fix this?

 

According to your sig - You have 2 trans ams. Sweet! Ok, start with swaping gauge clusters with your other TA. If the tach reads fine from the other one then your tach that was reading double was probably bad and should then be replaced.

 

I had the same problem today. I went to jump my brothers car and I started mine up and noticed the tach was reading double. After he took the cables off. It was still doing it. He said I need to tighting the cables since they where loose. I did and it's back to normal like it was the day before. I don't know it that's your problem but it's worth a check. Adam :-)