65 Valiant oil light only flickers when key turned

I'm trying to figure out why the dash oil light doesn't stay on when I turn the key to on. It will only flicker for a second when you turn the key from ACC to OFF or from OFF to ACC. It's a new switch and cylinder. I wasn't getting any dash illumination so I took out the instrument cluster, replaced the bulbs with Yellow LED bulbs, BAD IDEA by the way, they are not even as bright as the regular 194 bulbs, and I also checked the orientation of the wires to the socket plug. It appeared some of the wires might have been in the wrong place on the socket plug so I went in order with my wiring diagram and when I got to the last one it was supposse to be a Dark Blue wire for the High Beam Indicator bulb, which also doesn't light up. However, I only had a black wire and a gray or light green wire left. I couldn't tell if the wire was light green or gray because it was so faded. I did change the harness and I'm not sure what car this harness came from. I think it may have been a 65 Barracuda. So I chose the black wire for the dark blue wire and it appears to go to the dimmer switch on the floor but that doesn't illuminate either on the dash. If the oil light flickers when you turn the key back and forth what does that mean? I tried to unplug the wire at the switch and jump it to see if the switch was bad but it didn't light up still. Could a wire be in the wrong location on the instrument panel plug or is it losing a ground when turned to ON?