Is my tach run through my alternater?

[bluecollerboater]

I have a 1985 Volvo penta AQ260A my tach (the original US Marine and no not the star wars just analog)has not worked since I bought the boat(1985 23.5 Bayliner Ciera). Looking at my coil there is no grey wire connected to it at all. In the main harness connector on the back left side of the engine there is a grey wire that runs along the back of the engine and up the right side to the alternator. It then plugs into a purple wire with a resister which is connected to the alternator. I am getting power to the tach I checked it with a meter, I even got the light to work. So I am assuming it is a signal problem. I have gotten everything else on this boat to work so the tach not working is driving me crazy. Any help would be greatly appreciated.

 

[Silvertip]

Re: Is my tach run through my alternater?

No! The "send" signal on the tach comes from the ignition on an I/O (auto style engine ignition).

 

[Don S]

Re: Is my tach run through my alternater?

Your tach should be getting a signal from the - terminal of the coil through a gray wire going to the S terminal of the tach.

You shouldn't have a gray wire on the alternator with the resistor. May not be an OEM wire, or faded, or ???? But it's not supposed to be gray, should be red.

 

[n_waite]

Re: Is my tach run through my alternater?

I have the same purple wire with resistor coming off of my alternator. I believe(I am doing this from memory so could be incorrect) that it connects to a dark brown wire, which then goes into the main harness plug. I haven't traced it up to the helm yet, but in the wiring schematic it show it splicing into another wire near the ignition switch? What is this wire for? I ask because the wire pulled out of the resistor and I can't find a replacement. Any ideas where I could find one? I think it says nartron on it and the resistance is 70 ohms. The only thing that I could think of was to run the hour meter, but with the wire disconnected I can hear the clock click on when I turn on the ignition. Is it for the volt meter? Will the boat run with this wire disconnected? What will happen if I hook it up without the resistor?