One other simple test is to remove the wire that goes to the sending unit at the connection on the back of the gauge.
When you turn the key on the gauge should read full.
If it does not there are 4 areas to check.
- Is there a full 12 volts at the gauge? I assume there is some voltage because you do get the 1/8 reading.
- Ensure that the gauge is grounded properly through the instrument cluster to the chassis. You can check that with a jumper wire connecting the back of the gauge housing to the chassis.
- The needle is sticking against the bezel because it is a poorly made reproduction unit. If that is the problem follow Phil's instructions. I fought that same problem last year on a '49 3100.
- The gauge is defective. If you can find a NOS gauge it will avoid the aggravation of the needle sticking. Some people have removed material from the gauge bezel so the needle has room to move.
