Alternator- tachometer

[rtchina]

Can anybody help me? I have a Yanmar with Yanmar engine control panel, and the digital engine hours meter has stopped working. I need a quick fix with an aditional engine hours meter, which I have purchased, but don't know where to connect. I am guessing that one output from the alternator provides this, ie when the alternator is energised, the clock runs. Am I correct, and is the negative just picked up from the bus??
thanks

 

[earlybird]

It is more usual to feed the hours counter from an "ignition switch" terminal powered when the key is turned on. The counter might well work from the alternator output but, depending on the charging set-up, would probably count all the time that the battery master-switch was turned on.
Negative is from the bus.
Add:- can't you just feed it in parallel with the existing counter?

 

[oldsaltoz]

Almost all tachometers are fed from the alternator, most engine hour meters are fed from the oil pressure switch.

Hope this helps.

 

[rtchina]

Many thanks, I'll try to work it out.
Roger

 

[mainmarine]

Some hour meters if combined in a tachometer only work if the tacho is also working, if you have an early alternator there may not be a tacho tapping on it but it is quite a simple job to take a tapping, off the alternator, for a tacho.

 

[VicS]

various generalisation above about how tachos and hour meters may be wired.

You dont say which Yanmar engine you have ... I have several wiring diagrams but without knowing which engine I do not know which to look at!

A quick glance at them though reveals that the hour counter, where fitted, is simply wired in across the power supply to the tacho. The power is on and the hour counter runs once the "ignition" switch is switched on.

Some tachos get their signal from a sensor on the engine, some get it from the "P" terminal on the alternator.


You cannot connect your hour counter to the alternator output. If you do it will run all the time the battery isolator switch is closed! It must be to a circuit that is controlled by the ignition switch.

 

[rogerthebodger]

Moat engine tacho's are in fact VDO. There has been some posts that advise if the hour meter in the tacho stops working , which it seems is a common fault can be solved by putting the tacho in your hot water cylinder cupboard.

If you wish to connect a separate hour meter you can take it off the oil pressure switch with a relay to reverse the signal or by using rectifier the to change the AC you get from the "P" terminal on the alternator to get DC which most hour meters need.

 

[DogWatch]

Can anybody help me? I have a Yanmar with Yanmar engine control panel, and the digital engine hours meter has stopped working. I need a quick fix with an aditional engine hours meter, which I have purchased, but don't know where to connect. I am guessing that one output from the alternator provides this, ie when the alternator is energised, the clock runs. Am I correct, and is the negative just picked up from the bus??
thanks

As already said, the engine hours should be connected to the ignition switch.

 

[rtchina]

I guess I have to be a bit ore specific about this. I want to fit the new engine hours meter at the nav station. If I connect at the switch, it is quite a long run down so clearly would be better to connect somewhere on the engine, which is a Yanmar 4JH4. When the ignition is turned on, then something on the engine must go live, and that I guess is where to connect, but what goes live?

 

[Fr J Hackett]

As many have said use the oil pressure switch.

 

[VicS]

There are very few places on the engine where you can pick up a supply that is not on all the time. The oil pressure switch is one of them. It will then be powered via the oil pressure warning light ... Hopefully that's not an LED or that idea may not work!
Unlike the normally wired hours meter it will not simply run when the key switch is on , it will only run once the oil pressure warning switch is open ( and the warning light extinguished)