Tachometer trouble

[tigertacos]

Ever since I bought my 260z my tach has decided it has never wanted to work.  Being that my car is an auto, it hasn't been too much trouble until now.  However, a recent decision to attempt a manual swap and my general annoyance growing, I have decided to fix it.  The issue initially seemed to be a connection issue, as the tachometer would occasionally come back to life mid drive and decide to work perfectly for me, apparently at random times.  I took the dash off, cleaned all the tachometer connections, and reassembled everything.  While the tach was out I tried my best to bench test it, with various methods, and couldn't seem to find a way that worked.  The tach still works occasionally, but not too often.  Before I continue ripping things out and go as far as to replace the tach, does anyone have any wisdom or prior experience to share with me.  Thanks

[SteveJ]

While the tach is out, you could use a meter like this one to test the signal going to the tach.

https://www.amazon.com/gp/product/B0002LZU7K or https://www.amazon.com/Mrcartool-Digital-Multimeter-500-10000-Temperature/dp/B07VKLKDZL

Connect the positive lead to the blue wire and connect the negative to ground. Put the meter on 6 cyl and start the car. If the signal isn't consistent, then you have a different issue to track down. If the signal is good, your tach is going bad.