The cluster is out, you won't believe what I found
The oil light should be a separate assembly. On mine, you can see it hanging loose, the black plastic. It is not grounded. it receives switched 12V on one wire, and the other wire goes out to the oil sender, which applies a ground when no pressure.
Use your ohmeter to trace the gauges path. As I said, on mine, the IVR contacts were not making contact with the board traces. The nuts might be loose / corroded. And, the gauges might be bad. "Fire them up" with a 1 1/2 V AA, C, or D cell
A 3V battery (two 1 1/2 V cells) will give you nearly full scale on the gauge
The oil light should be a separate assembly. On mine, you can see it hanging loose, the black plastic. It is not grounded. it receives switched 12V on one wire, and the other wire goes out to the oil sender, which applies a ground when no pressure.
Use your ohmeter to trace the gauges path. As I said, on mine, the IVR contacts were not making contact with the board traces. The nuts might be loose / corroded. And, the gauges might be bad. "Fire them up" with a 1 1/2 V AA, C, or D cell
A 3V battery (two 1 1/2 V cells) will give you nearly full scale on the gauge