I have a 1995 S-10 that is standard without a tachometer. I went to the junk yard and bought an instrument cluster with tach and the tach would not work. The tach needle does go to 0 every time the key is turned on but nothing else. Thinking the tach was bad, I was able to try another instrument panel with the same results. I did make sure that my harness plug has a good tach signal because I hooked up an aftermarket tach and used the tach signal in the harness and I was able to get an accurate tach reading. I also thought that the my tach signal might not be aligning with the instrument cluster but I did check that out and it is going to the right connection. So much so that I am able to get a good tach reading from the back of the instrument cluster where the words "tach" are. At this point, I am stumped as to how to get a a factory tach to work. Any help?