Yanmar Tach Reading Way Too High

[Wotname]

Originally Posted by BruceS

You said you cleaned the sensor? What with & did you remove the sensor to do it?
Cleaned the contacts? What contacts exactly? I believe it's simply a magnetic pulse & no contact what so ever.
Keep us informed please?

The wiring loom uses spade terminals which push onto the contacts/terminals of the sensor.

[RaymondR]

My understanding of these magnetic reluctance transducers is that they put out a sine wave signal the frequency of which is proportional to the number of teeth passing the transducer in a fixed unit of time.

The sine wave ifs generally passed through a Smidt trigger to condition the pulses into an electronic circuit which feeds a finite amounts of current into a resistor capacitor filter the voltage of which is dependent upon the balance between the quantems of current being fed in and that being drained out by the resister. The chip I'm familiar with is the Texas Instruments LM2917 frequency to voltage converter but I'm working with a pretty decrepit old memory so can't be certain.

Consequently a higher reading would tend to indicate more pulses getting to the readout or the resister going higher resistance or the capacitor lower capacitance or an out of adjustment volt meter.

[sailorboy1]

Well I noticed the other day the the tach reads 500+ rpm with the engine off. I haven't done any work troubleshooting the issue yet as I have other things more important to me to do. But I ran the engine yesterday and the rpms seemed to track being 500-600 high, ............... till it decided not to. After warming up and at idle the tach was reading around 500 rpm high, but the reading was surging (the engine wasn't and was just purring away). I think my tach has gone bad, which pisses me off as it is only 3 years old.

[sailorboy1]

Said a voodoo chant and it appears to work now. But since it now has a spell on it it goes crazy every once in a while.

So if you are reading this to fix your similar problem all i can suggest is a good witchdoctor.

[jimbunyard]

Originally Posted by sailorboy1

Here is the thing:
- the tach was working fine
- due to a leak above the sensor it was shorting and reading low
- fixed the leak, clean the sensor contacts, put new spade connectors on the wires
- now it reads high

I am resistant to messing with unscrewing and missing with sensor clearance till last resort.

You don't say what was leaking but I'm betting it was water and not oil. If so, I'd say the sender is internally contaminated; it may eventually dry out and work ok, but if it was salt water contamination, the sender probably won't last long.

Automotive sensors that run off the flywheel often come with a stick-on paper 'spacer' that sets the proper clearance; you just install it to lightly contact the designated surface, and when running the spacer gets knocked away by the rotation of the flywheel.

[Sailmonkey]

Originally Posted by sailorboy1

Said a voodoo chant and it appears to work now. But since it now has a spell on it it goes crazy every once in a while.

So if you are reading this to fix your similar problem all i can suggest is a good witchdoctor.

You’re going to need some chickens onboard to maintain the efficacy of your voodoo enchantments.

[sailorboy1]

Originally Posted by Sailmonkey

You’re going to need some chickens onboard to maintain the efficacy of your voodoo enchantments.

And lots of rum

[sailorboy1]

Originally Posted by jimbunyard

You don't say what was leaking but I'm betting it was water and not oil. If so, I'd say the sender is internally contaminated; it may eventually dry out and work ok, but if it was salt water contamination, the sender probably won't last

Been working 3 years. So i would I would bet you are wrong.

[jimbunyard]

You mean 3 years after the leak? Doesn't seem to be working so well now, or is one of us chronologically challenged here?

Was the leak oil or water?

[sailorboy1]

I am so not challenged that i am not responding to your question looking for fuel to argue.

[jimbunyard]

Then I guess the whole post is meaningless; i.e. you're not really looking for an answer to your 'problem', if there ever was one to begin with.

[sailorboy1]

Nope, i fixed it.

[Wotname]

Originally Posted by sailorboy1

Nope, i fixed it.

Just to be clear, did you fix it solely with at the voodoo chant?

And have you fixed the " it goes crazy every once in a while"?

If so, please tell how as it will be very helpful for others!

[sailorboy1]

Originally Posted by Wotname

Just to be clear, did you fix it solely with at the voodoo chant?

And have you fixed the " it goes crazy every once in a while"?

If so, please tell how as it will be very helpful for others!

Yes and yes.

It took a second voodoo chant to calm the crazies down. Pretty much like medicine where you need a second drug to counter the first.