Hey everyone,
new to the forum and was hoping to get some help since I’m out of ideas

First a little about the truck.
it’s a 94 T100 4x4 DX Manual Trans with the 3.0L V6

Below is comparison of the original cluster with no tach and the new/used cluster with a tach.
note: everything works with the new cluster but it shows 3000RPM when the timing light shows 1500RPMs
i know there is a blue potentiometer that appears to have a Phillips screw and I thought I read u could adjust the rpm this way but to access it you would have to take the rpm faceplate off so not sure how am I suppose to adjust this tach so it’s correct?
any ideas is super appreciated

  

Looks like I may have stumbled onto a solution that appears to be working

So I read somewhere that I adjust that potentiometer to 44.9k ohms resistance when measuring on the back side of the tach. Well when u turn as far as u can it’s 43k at the most and when we tested it was 4000 rpm right from the get go.  Then I was like, it was at 33k ohms and rpm was 3000 and then 43k it’s was 4000 and with my timing light I can see it’s actual 1600rpm so change the password ohms to around 18k and it should read about right.

bam! Worked like a charm