I've been having trouble with my tachometer reading in the past few months. At first, it just started to jump around a bit, then it would fall to zero and read nothing for hours, just to start jumping around again. About two weeks ago, I was driving home at night, and out of nowhere my stereo speakers stopped working, and my display and headlights got about twice as bright (which I can safely assume is the brightness they should always have been), and the tach came on and stayed on, reading the correct RPM's. Then, everything dimmed again and the stereo came back on. This happened a few times, like someone was flipping a power switch on and off, where off to the headlights, display, and tach was the on switch to the stereo.
I cleaned the connections on the alternator, and also checked the connections in the dash to the tachometer. Now, instead of jumping around, the tach is either on or off, and headlights and display are either the brightness they should be, or half the brightness [&o]. The stereo doesn't come in and out like it did that first night, but I'm just curious if anyone had any ideas about how to keep everything the way it should be; tach on and headlights and display as bright as they should be. Any ideas would be appreciated, thanks!

 

Sounds like you need a new alternator.
The tach runs directly off the alternator and when it goes bad the tach stops working, the lights will dim because the battery is going dead.
Had you not said that you tightened the wires on the bgack of the alternator then I would have said that you have a lose wire, but you tightened them and still nothing.
So your alternator is toast.
Go to any autoparts store and have them test it, after you charge your battery of course.

 

Thanks for the input, I'll look into doing that