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Tachometer

terry_thatcher

Terence Thatcher
I run a Balmar large case alternator and regulator. For the last couple of years my tachs stop working after a couple of months; the tachs run off the alternator. I have a Perkins 4-108. I have replaced the sending wire, to no effect. Suggestions on why I am killing my tachs? Can I run a tach off of some other part of the engine, rather than the alternator?
 
Are you connecting directly to the alternator, or to the tach output on the regulator? You could measure the voltage output of the alternator (or regulator) and see that it is in spec, and not more than what the tach requires.
 
Terry,
I'm no expert on large case Balmar alternators, but I think you can feed your tach with your external Balmar regulator (if you are using one). My ARS-5 regulator has a tach input post, from the alt. stator, providing the pulse signal, and a tach output post feeding the signal to the tach sensing input.
 
Good suggestion, John. Thanks!
I think I'm experiencing EMI interference from the alternator. The needles on my oil pressure, water temp, voltmeter and ammeter, as well as the tach, are all jumping around. John, do you know if the TinyTach is immune to EMI? I'm thinking that I have to shield the instrument wiring, but I don't know what works best. I used to use an automotive alternator that didn't interfere with the instruments,, but changed it out for a 105A Leece Neville with the Balmar ARS-5, and now have instrument jitters. John or anybody else have a solution?
 
This is just a thought that came into my pea brain.
We have used "Tach Filters" on some race cars to allow a accurate signal. It is just a tiny box that wires into the tach cuircut. Ths was when using electronic ignititions. I'm not sure how it works or what it affects. It's magic. I have not dealt with the problem you have on boats. But think it may be a similar situation. I may be wrong though...
Mitchell
 
Good suggestion, John. Thanks!
I think I'm experiencing EMI interference from the alternator. The needles on my oil pressure, water temp, voltmeter and ammeter, as well as the tach, are all jumping around. John, do you know if the TinyTach is immune to EMI? I'm thinking that I have to shield the instrument wiring, but I don't know what works best. I used to use an automotive alternator that didn't interfere with the instruments,, but changed it out for a 105A Leece Neville with the Balmar ARS-5, and now have instrument jitters. John or anybody else have a solution?
I doubt it is EMI. Gauges should be immune to it. It sounds to me like a bad connection somewhere. Or, if the regulator or alternator is malfunctioning and is putting out a pulsing voltage. (failed diode maybe?) Do all of your gauges share a common ground point or power point? Or perhaps a bad connection on the alternator?

Car tachs are fed from the ignition, and multiple spark type ignitions used in high performance engines could cause issues. That's probably what the filter was for-to filter several fast sparks into a single pulse. It would not be applicable on a diesel engine.

Tiny Tach sounds intriguing.
 
Another thought on how we use our boats.
I have devolved to day sailing. SF bay is great but it's just not the BVI's.
In and out of the same marina. The batteries are charged when I leave the dock. OK So why the alternator. I turn off the voltage regulator
I have 4 (100ah) LiFePo4 's. No separate starting battery.
 
Warren, I had wondered if this (filter) crossed over to diesel. Something I am fairly unfamiliar with at this point. Indeed, the filters I mentioned were on Multi spark type ignition systems. Diesel is totally different in Ign. And, come to think of it most of the cars I've dealt with, don't even have alternators.
"nevermind"
Mitchell
 
Thanks for the input from all. Turns out that all the grounds were connected and tight, but I had run the gage cluster ground to the alternator ground post, like it was done with the previous automotive unit. The new Leece Neville alt post also serves as the ground for its field exciter, which apparently feeds in a pulse train that gauges don't appreciate! I spliced in a new wire for the gauge cluster to the negative bus at the same post of the regulator, and that fixed it. All qauges are now rock steady. The alt function was never affected, as far as I can tell.
 
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