Driving my 71 series 3 this past weekend I noticed my tach stopped working. Then realized that ALL the gauges had quit as well. Car is still charging well, starts well etc. My first thought is that the ignition switch has gone bad but thought I would ask the forum. The ignition switch appears the common denominator in the wiring diagram

 

Not familiar with S3 wiring but I would think the ignition switch also powers the fuel pump, alternator relay and other things the the engine needs to run. Check your fuses. On my S1.5, fuse 7 powers the things you mentioned.

 

I'll do that. I had my pocketknife with me and tried jumping across the fuses while on the side of the road just to see, but that didn't work. I'll get my test light after it

 

On my series one there is a ballast resistor behind the dash panel that failed.