Originally Posted by Phak1
It looks like your resister may be mounted in the wrong place. My resister is mounted on the positive lead going to the gauge from the ignition switch, cutting the voltage so the gauge doesn’t see 12 volts. Your picture shows a resister mounted on the wire going from the gauge to the sending unit so your gauge see 12 volts then gets cut down to protect the sending unit. You may have burnt out the original 6 volt gauge so that may be why it is not registering.

Can you post a photo of yours so I can see how it should look?