Hello, I am working on my brother-in-laws totally stock 240z. He was driving it a few months ago and the tach started pegging the gauge. It would only do it when it was hot outside. All of a sudden last week the tach just went to zero and so did all of the other gauges except the amp meter. He also lost the turn signals. We checked the fuses and all looked good and also removed the fuse block to make sure that there was no corrosion below the fuse block. It looked like new and there was no signs of corrosion.
Can anyone think of something that would cause this? Is there a common ground for all of the gauges? If so where might we find that.
Thanks for all of your help,
Take care and have a great day,

I just enlisted my club's electrical guru on this. I'll let you know what he says.

Check your grounds and recheck your grounds!
I think your gauges all share a common ground.
That's where I would start anyways, Hope this helps.

Mystery solved! It was about 30+ years of crud built up around one of the fuses so that the power would not exit the fuse box. Electrical problems suck! Thanks for the advise.