89 Mercury Black Max Tachometer not working

[mkniese]

I swapped a blown up xr4 for a running xr4 Black Max having to transfer the harness and everything went well except, I do not have a tachometer now. I have checked that the gauge has power, when I turn the power on I can see the needle even drop to zero. When I crank the motor I and it fires the gauge does not give me a RPM reading. I have checked wiring trying to see if I made a mistake or if something is crossed up but nothing is jumping out at me. I have the Gray wire which I believe to be the tach. signal wire connected but still nothing. Anyone have any ideas? It would be greatly appreciated before I go bald pulling my hair out....

 

[Chris1956]

Grey wire should be connected to the AC side of the rectifier or voltage regulator (whichever you have). It is possible a shorted rectifier would kill the tach signal. Disconnect the yellow wire from the rectifier and connect it to the grey wire and see if the tach starts to work.

 

[mkniese]

Thanks for the response, I have a voltage regulator gray and purple wires coming out of it, two yellows from stator and one red to battery. It charges the battery I see the gauge move with rpm's, I took a multi meter and measured 14v on the purple wire and 9v on the gray. I would think that the 9v would be the pulses to the tach? Not too sure about anything, getting confused..

 

[mkniese]

So I connected the gray wire to one and of the yellow wires coming from the stator and the tach is working again.
Many thanks for the help, just couldn't get past as to why all of a sudden it stopped working.

 

[Chris1956]

The grey wire on the VR is connected directly to one of the yellow stator wires. It is supposed to make the wiring harness one-to-one, and color coordinated.

 

[mkniese]

Ok now it's starting to make sense, being that I didn't have a rectifier, I was unsure of what changes inside the regulator. Thanks again.