Driving home last night, I noticed something odd. Even though I was cruising at 55mph, my tachometer said 0 RPM. Holy ****!, I thought, I'm getting AWESOME gas mileage now!

Then the cobwebs of a long day at work shook from my brain, and I realized my tachometer wasn't working. At the next intersection it jumped to 800RPM and stayed there at idle. I put it in neutral and goosed it a bit, making it jump like it should... except it was odd. It'd jump to 1500, then shoot to -100, then jump to 500... for the rest of the drive home it did this, jumping all over the place.

Today it worked fine.

I'm thinking the humidity last night got to something. Probably a loose connection somewhere. Where should I look?

 

If it's like my tach, there should be a wire going into the dist. it might be loose or corroded.