Instrument lights don't work

65 Dart 270.

I did a search and reviewed all the threads I could find regarding people with no instrument lights. I tried several of the remedies to no avail, even putting in a new light switch.

My problem is that the gauge backlights aren't working at all. First check was to the fuse block, the fuse looks fine. I cleaned some corrosion from the contacts and moved on. I removed the instrument cluster and checked each bulb and the contacts, everything seemed fine, although I replaced two bulbs just in case. No joy. I then put in a spare switch I had. Oddly enough, this switch caused the blinker lights and high beam light to stay on and dim with the rheostat, although the gauge lights still would not come on. I changed back to the old switch.

Currently, I have: Headlights, parking lights, brake lights, dome light, blinker indicators, high beam light indicator and oil pressure light. The only lights not working are the ones behind the gauges. There is some corrosion in the rheostat, and I've tried spinning it repeatedly and watched the dust fall out. Still no changes.

Any help would be greatly appreciated.

Also noticed there is a red wire in the fuse block that has been cut. Can anyone tell me what the wire goes to? Could that be my problem?