New Autometer Gas Gauge Problems

I just put in an autometer fuel level gauge & am wondering if it's normal for the needle to move back & forth around 1/8 of a tank. It seems to do this whether I am moving or not. When I initally installed it did seem it read around an 1/8th too low & so went to fill up & it didn't go to full. It stayed between 3/4 & full. Although when I drive or sit an idle for a bit the needle will move all the way to full for a bit. SInce I never had a working gas gauge I don't know if it's normal. BTW, I did get the correct gauge for the stang it's the up to 1985 one I believe 70-12 ohms.
 
Sorry I didn't see the range in the orig post.

It sounds like you're getting extra resistance somewhere. How old is the sender? Check the grounds and the integrity of the sender lead going back. Where are you getting the power source for the gauge?
 
mdjay said:
Sorry I didn't see the range in the orig post.

It sounds like you're getting extra resistance somewhere. How old is the sender? Check the grounds and the integrity of the sender lead going back. Where are you getting the power source for the gauge?

The sender is original. I used the orignal ground that the voltage regulator used & the power I took from the old gas gauge. Just took out the voltage regulator for the gauges so I would have constant 12volts. Actually, the only gauge working in the dash right now is the speedo. I have a temp & oil presure gauges mounted under the radio. I'll check the grounds & change them & also the connections.
 
If all else checks out between stable power and "good grounds," my guess is the sender... Especially if it's that old with a brand new gauge that is more accurate. However, you may have an issue in the lead from the gauge to the sender. Test if you have any excess resistance in that lead before going directly to the sender...