My Tach just started working but with a bad Rectifier

[jammer]

If possible. Could someone explain what just happened.

Two things.

First when I was out boating today my Tach, which wasn't working started to work. Or at least act like it is. I say act because I am told I have a bad rectifier on order. I've had the boat out for about 4 times and ordered a new tach..it didn't work...so I had the dealer check for what happened when I tried to get it working and I was told it has a bad rectifier. The only thing which has changed is I replaced all the old 3amp fuses. They were getting corroded and I just replaced them. Now the Tach began working after about, I would say, 10 minutes on the water. Does this mean that my battery is now charging? I have a volt guage but that will be part of my second question. The tach isn't working right because I notice now and then that it pegs itself at 7k.

I also noticed the Speedometer works most of the time. In really choppy water it sometimes doesn't register.

The volt guage on the boat I was told was old and should be replaced. I looked over the instructions and it read as though it just needs ground, power for the light, and I. When I pulled the guage there is ground, I, and another. I don't know what the other is but it isn't labeled S on the guage. Any ideas? The Teleflex guage I have has a cover over the S with special notations in the instructions for the S terminal.

Thank you.

 

[ricksrster]

Re: My Tach just started working but with a bad Rectifier

Your speedometer probably works off a pitot. Water pressure in the tube connected to the gauge gives the speed reading. If you are in choppy water , the pitot is probably coming out of the water. The pitot is either located on your motor leg or fastened on the transom toward the bottom of the boat. It may not be low enough or the chop just enough to take it out of the water.
As far as your tach goes:
http://ww2.tflx.com/PDF/99320.pdf
http://ww2.tflx.com/pdf/obtach~1.pdf
The other post on your Volt meter could be for a light.

 

[jammer]

Re: My Tach just started working but with a bad Rectifier

Thank you. I see in the pdf that recifier may not be working properly. Can they just..go from not working or not giving volts to kinda giving volts though?

My speedometer's pilot is located on the transom. Are there different ones of these for different guages?

 

[WillyBWright]

Re: My Tach just started working but with a bad Rectifier

A full-wave rectifier contains four diodes. One or two can fail and it can still work as a half-wave rectifier. It charges with half the current when that happens. Suddenly pegging and intermittent readings tell me you have a bad tach. Loose or corroded connections can cause intermittent readings, but not pegging. Loose, corroded, or crossed battery connections are the leading cause of rectifier failures.

Voltmeters don't typically use the S terminal. They just read volts via the Gnd and I. The third is just for the light and nothing else. Since they use a common case for most gauges, it might have a S terminal on it, but it serves no function. The mystery terminal is probably an unlabeled S because it's not needed. I've also seen a few that have separate Gnds for gauge and light.

 

[jammer]

Re: My Tach just started working but with a bad Rectifier

Willy or anyone..what about the other question on the pilot. I used the pilot that was already on the boat and connected the tube to the speedo. Are there any differences in pilots?

 

[jammer]

Re: My Tach just started working but with a bad Rectifier

Here is the final that was found about the tach starting to work.

First the rectifier needed replacement. Now the tach. On the fly wheel...of the 4 magnets on it..or diods...they were shattered. The two for the ignition were there. Close as anyone could figure there were pieces of these magnets in the fly wheel somewhere. I've never heard of such a thing. Well anyway what we did was to re-epoxy the magnets in place. Tach works fine now.