Yanmar rev counter stopped showing revs; sensor or tacho problem?

[tudorsailor]

I have a Yanmar 4JH3-HTE engine. The rev counter has stopped showing the revs. How do I determine whether its the sensor or the tachograph that's at fault?
Indeed where do I find the sensor on the engine (I cannot seem to find a diagram that shows its location). I have read elsewhere that the contacts can need cleaning.

Thanks

TudorSailor

 

[rogerthebodger]

I have a Yanmar 4JH3-HTE engine. The rev counter has stopped showing the revs. How do I determine whether its the sensor or the tachograph that's at fault?
Indeed where do I find the sensor on the engine (I cannot seem to find a diagram that shows its location). I have read elsewhere that the contacts can need cleaning.

Thanks

TudorSailor

Is this any help

http://www.cruisersforum.com/forums/f54/where-is-the-tachometer-sensor-on-a-yanmar-4jh3e-23223.html

 

[RichardS]

On my Yanmars the tacho "sensor" is a yellow wire which comes out of the side of the alternator. When one tacho stopped working it was just a dirty bullet connector on this wire.

I've no idea if yours is the same but a quick re-make of the alternator connectors might sort it.

Richard

 

[PuffTheMagicDragon]

Follow the wires and thoroughly clean all connections.


P.S. The usual 'culprit' is the wire that picks up the pulses from the alternator, if yours is of that type.

 

[VicS]

On my Yanmars the tacho "sensor" is a yellow wire which comes out of the side of the alternator. When one tacho stopped working it was just a dirty bullet connector on this wire.

I've no idea if yours is the same but a quick re-make of the alternator connectors might sort it.

Richard

Follow the wires and thoroughly clean all connections.


P.S. The usual 'culprit' is the wire that picks up the pulses from the alternator, if yours is of that type.

The wiring diagram in the Operation manual http://www.yanmarmarine.com/theme/y...ual/Operation-Manual_4JH3DTE-49961-202851.pdf shows thath the siganl wire is an orange wire and that there is an engine mounted sensor. The signal does not come from the alternator!

The link Rogershaw has already provided provided in #2 includes a photo of such a sensor mounted on the flywheel housing. http://www.cruisersforum.com/forums/attachment.php?attachmentid=6942&d=1233439165

 

[charles_reed]

Unfortunately Yanmar have a reputation for dodgy wiring to their control units - my rev counter (alternator drive) has come and gone - the hour meter has shown gibberish and now (whilst the 1st two have been got going) the warning lights and siren for overheat and low oil pressure have disappeared.
It usually has to do with a poor earth-return.

 

[rogerthebodger]

The wiring diagram in the Operation manual http://www.yanmarmarine.com/theme/y...ual/Operation-Manual_4JH3DTE-49961-202851.pdf shows thath the siganl wire is an orange wire and that there is an engine mounted sensor. The signal does not come from the alternator!

The link Rogershaw has already provided provided in #2 includes a photo of such a sensor mounted on the flywheel housing. http://www.cruisersforum.com/forums/attachment.php?attachmentid=6942&d=1233439165

The question is how many wires go to the tachometer itself.

If there are 3 +12 negative and signal then it most likely will be alternator driven but could be pulse driven from a inductive sensor located on the flywheel housing.

If there are only 2 wires to the tachometer it will be tachogenerator driven, driven from somewhere from a rotation part on the engine.

I have both my tachogenerator is driven from a shaft on the back of the injector pump and the alternator is driven from an output on one of my alternators.

https://www.vdo-instruments.com/sen...-sensors/generator-sender-7-8-18-4-pulse.html

inductive sensor.

https://www.vdo-instruments.com/sen...nsors/inductive-sender-magnetic-pickup-2.html

From the manual Vic poster it looks like an inductive sensor so will look like this

Tachogenerator wiring diagram

Alternator driven tachometer wiring diagram.

 

[tudorsailor]

So partly to answer my own post - and so might helps others, I have found that the service manual for the 4JH is online such as here. This has a better picture and explanation of the tachometer


There is a trouble shooting guide.
First it says "check if there is an open-circuit cable connection at the rear of the meter.... now I need to understand what an "open circuit" connection means.
Next it says "measure the voltage between the cable terminals (To be 10~16V)" Am I right in assuming this means when the engine is running!
Next measure the internal resistance of the sender (to be 1.6 ohms)
Next measure output voltage of the sender (to be 1V or higher)

So lots to do when next on board in 2 weeks!

TudorSailor

 

[VicS]

So partly to answer my own post - and so might helps others, I have found that the service manual for the 4JH is online such as here. This has a better picture and explanation of the tachometer

There is a trouble shooting guide.
First it says "check if there is an open-circuit cable connection at the rear of the meter.... now I need to understand what an "open circuit" connection means.
Next it says "measure the voltage between the cable terminals (To be 10~16V)" Am I right in assuming this means when the engine is running!
Next measure the internal resistance of the sender (to be 1.6 ohms)
Next measure output voltage of the sender (to be 1V or higher)

So lots to do when next on board in 2 weeks!

TudorSailor

It means a disconnected or broken connection.

Resistance of sensor should be 1.6k ohms! ( 1600 ohms)

The engine need not actually be running to check that there is power to the tacho but the key switch ( or wahtever you have in place of a key switch) must be in the normal running position ( in other words "ignition" switched on) but the buzzer will be very annoying!

I assume you realise that the 1 volt output from the sensor ( engine running) is AC ..

 

[djc]

My Yanmar Rev counter stopped working on my 4JH2E all of a sudden , a few years back , found cleaning the wire and sensor terminals at sensor as per your diagram done the trick . It dosent help that yanmars fit a sea water drain tap above the sensor and sea water muck & crud can find its way to the sensor area. if not careful .

 

[tudorsailor]

It means a disconnected or broken connection.

Resistance of sensor should be 1.6k ohms! ( 1600 ohms) Ah ha, hadn't spotted the k

The engine need not actually be running to check that there is power to the tacho but the key switch ( or wahtever you have in place of a key switch) must be in the normal running position ( in other words "ignition" switched on) but the buzzer will be very annoying!

I assume you realise that the 1 volt output from the sensor ( engine running) is AC .. DId not appreciate that - thanks

Thanks for the above

Tudorsailor

 

[tudorsailor]

To resurrect this post.... After last year's post the rev counter started to work without my doing anything to it.
We are on board for the first time this year and it's not working again. There is current going to the rev counter. So does this mean it's dead?
Thanks
Tudorsailor

 

[RichardS]

View attachment 64230
To resurrect this post.... After last year's post the rev counter started to work without my doing anything to it.
We are on board for the first time this year and it's not working again. There is current going to the rev counter. So does this mean it's dead?
Thanks
Tudorsailor

As per the answers last time, it's probably a poor connection and if there's power going to the back of the dial then it's probably the connection on the engine sensor or an in-line connection somewhere along this cable between the sensor and the dial.

Richard

 

[pandw]

Hi Tudorsailor - Did you fix your problem and how?

I also have a Yanmar 4JH4-HTE, with a tacho problem. No rev counter and the hours flash when engine is running. The hour display is backlit.

I seem to have 13V to the Tacho, and there is about 6V and 130Hz on the orange wire running from the alternator to the tacho.

Any suggestions?