3 broken tachs?

[Ashton_1012]

Hey everyone, im dabbin into electrical, the black hole that i have no knowledge of. So my problem is i either have 3 broken tachs, or my wiring is messed up. I had an old tach hooked up, and got a small one from a garage sale. It was in better condition, and it had different color back ground lights. I hooked it up in a parking lot, and it worked for about a minute, then just quit. So i thought i fried it by not isolating my connections, i was just checking to see if it worked. So i hooked up my old one that worked before, and it doesn't work. I had another one at home that i wasn't sure worked or not, that i hooked up. it too didn't work. So either all three of these are broken, or i have wiring issues. Ive traced all the wiring, checked all fuses, it all seems ok. I thought maybe the coil was bad, but i dont think there is anything that particular part of the coil is bad without the entire thing being bad. How can i test the wiring? i know the green wire that hooks to the coil works, because it shocked me!!

[1972hiboy]

You gotta make sure your hooking these up right. I would imagine they would be labeled on the tach either on the body or the wire. You need a 12v key on source one wire goes to the NEgative side of the coil and the other is for the tach light so you can see it at night. Some older tachs ive have seen in the past had batterys. not all or probably even most use batterys but its just a thought if these are old and funky.

[Ashton_1012]

well i know i had the first one hooked up correctly, the colors matched up exactly and i was running it for atleast 2 months. Then i had the new one hooked up, worked fine for a bit, then just shut off. so i hooked up the previous one that was working fine before, exactly how it was supposed to go and how it was before and it didnt work. no lights or anything. its got to be wiring, but i have no idea how to test it.

[1972hiboy]

hmm or bad connection? all the crimp fittings nice and tight? Id hate to think it was coincidence but stranger things have happened.