Tachometer Exciter Question

[rebuckley]

SO I got the new gauge/sender package from AD, quite nice. My Tachs are still not registering anything.
They do have battery power, and a good ground.
I assume it is the sender wire, not "sending". Which I assume means one of three things - Bad sending wire, bad exciter or an issue in the alternator itself. I am going to make a direct wire connection today - alt to tach - to rule out the old wire being the issue. Does anyone know how to test an "exciter"? Is there some way I can see if it is sending any information at all?
Is there something else I may not have thought of that coudl be the issue?
Thanks!

[mike66]

On my tach, the wire sends a pulsed signal at half the voltage, e.g. 6 volts.

[denchen]

My alternator didn't have a taco take off connection, so I soldered a wire direct to one of the primary windings before the rectifiers or voltage regulator. I put an inline 1 amp fuse as soon as the wire came out of the back of the alternator cover, and took this wire direct to the gauge. It all works a treat and has done so for 3 years now

[jleonard]

Here is the engine wiring schematic if you don't have it already.
Hopefully this will help you out.

[rebuckley]

Thank you all - I am thinking I may have an Oil Pressure switch issue now - so the Alt is not getting the signal to "kick on"? I am going to check connections (and the line for the tide today due to Hermine). Is there any kind of test I could do for the Oil Pressure switch? I know my Oil Pressure is fine (as those gauges and sender are new and reporting fine).

[jleonard]

If your alternator is charging the pressure switch is working. That's where the excitation voltage comes from.
You could bypass the switch and run 12 v direct to double check.
Also check your ground connections...the root of most evil regarding 12 v on a boat.
Both at the alt and the gage panel.

[rebuckley]

Thanks Jay -

So to bypass, I coudl run the 12v(+) direct to the alternator post (marked D+, on that schematic?), essentially isolating the Pressure switch out of the connections? That woudl then make the Tach Tap get the 6v pulse, if the Oil Pressure switch was faulty. Is my thinking correct?

Reb

[jleonard]

I believe that would work. Or with a short jumper just jump the switch itself.

[Nepidae]

Call Brian at AD with your questions. Both he and his father are very helpful with issues.

Did you by any chance take pictures before you removed the old gauges?

[rebuckley]

Yes, I did get pictures and have a copy of the AD schematic (which is more helpful). The Tach is responding now, although I have not calibrated it yet - I am not sure if the hours meter is working as I have not run it long enough to get it to register. I did bypass the low oil pressure switch, and found I had a bad ground wire - that fixed everything. The only issue I am still tracking is the lack of the "ignition buzzer". I assume it is either a missing ground, or The low oil pressure alarm wiring needs attention - as I removed it to install the new sensor.