Tach Erratic!!

[K-Dawg]

Are both gray wires from the rectifirer/regulaters supossed to be hooked up, or just one. The one on the bottom has a plug in it. Tach sometimes works but, most of the time reads incorrectly. Done a search but found nothing to help. I once saw a post on how to test r/r's something about unplugging them but, I don't know which ones to unplug or if I'll get shocked. Each one has 2 yellows 2 reds 1 gray. or do I have a jackup tach and need a new one. Any info would be helpful and appreciated. Motor is a 94 Mariner Magnum III 150. :confused:

[SportJ-US-1]

One grey wire at a time. Try swapping to the other grey wire. If still erratic, I would suspect the tach.

[K-Dawg]

Swapped gray wires same thing. This tach has done this since the install. just now it does it more often. Could it be a bad ground? When I run it on the hose at home it works fine, put the SOB in the water and does'nt work right.

[K-Dawg]

Ttt, Ttt

[gambling209]

if you swap to the other gray wire, check all connections, grounds, and it is still jumps around.it is time to buy a tach. you can put a frequency input in on it to check the tach. if its a teleflex i can give you the values, but you have to have a frequency generator.

[pyro]

Sometimes the loose connection is actually inside the tach. Try another tach.

[gambling209]

forgot to say that if your tach has a selector on the back. for like going from 4-6 cylinders ect. try turning it a few times. sometimes they get a buildup on them, making them jump.