Wasn't sure if this qualified as "Engine/Performance" or "Tech" so I'll start here. I'm a carpenter with some downtime over the holidays and figured I'd do some work on my gopher truck. While I'm waiting for my new body parts to arrive... The tachometer has never worked in my truck (I bought it used) and my old mechanic said he couldn't find a mechanical problem and said it was most likely the gauge. I found a used one and swapped out the whole cluster but no luck - all the other functions (fuel, temp, press, speedo) work on both clusters. I have a hard time believing the used one coincidentally has only the same non-working gauge as my original. From what I could find on the internet, the tach gets its signal (increasing voltage=higher rpm) from the top of the coil that goes to pin 31 on the 3rd harness at the control module on the firewall. I can't find any docs to figure out where it goes from there and the pinouts I could find for the black and white connectors into the back of the cluster make no mention of the tach signal. Any ideas???