Rev Counter failed - how to test for failure point?

Richard10002

Richard10002

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Some will recall that, whilst I was messing about with my alternator and charging regime, my rev counter failed.

It's failure coincided with removing the sensing lead from the alternator and extending it to sense at the domestic battery... all connections were made and unmade with the engine not running.

Most responses were that I must/may have disturbed a connection, but I have checked the connections in the vicinity, and remade them, and all seems OK, but the rev counter doesnt work so....

Is there a way of using the multimeter to test where the failure has occured.... e.g. if I can check that the alternator is outputting a signal, then I know it's further down the line etc.

also, is there a "something" I could connect directly to the rev counter, to see if it is working.... I understand it's an AC signal which runs the alternator, so maybe there is a way of feeding a variable AC signal of the right voltage or ampage or whatever, to see if it works.

I'm guessing a lot here, but I think those who know will understand what I am trying to do.

Many Thanks

Richard
 
you could put a meter on the output wire from the alternator and run the engine at low revs - you should see a fluctuation ... more expensive meters might react quicker, but my cheapo is enough to see that there is something happening there!

you could do a continuity test between the alternator output wire and the rev counter

you could do an earth test on the rev counter ...
 
Richard

I had same problem a few years ago and can't remember what the exact solution was but it was a termnation issue,

The motor crowd should be able to help
 
[ QUOTE ]
you could put a meter on the output wire from the alternator and run the engine at low revs - you should see a fluctuation ... more expensive meters might react quicker, but my cheapo is enough to see that there is something happening there!

you could do a continuity test between the alternator output wire and the rev counter

you could do an earth test on the rev counter ...

[/ QUOTE ]

Thanks for the quick reply! Bit double dutch to me at the moment, sorry:

meter on the output wire from the alternator.... one probe on the output, and the other probe where? (I' guessing the engine block, and should I be testing for AC volts, or what?)

Continuity - OK

earth test - what and how?

Cheers

Richard
 
[ QUOTE ]
but it was a termnation issue

[/ QUOTE ]

Is that a technical term, or was the rev counter "Terminated" /forums/images/graemlins/smile.gif
 
Sorry I had a connection problem of some sort can't remember what it was.

depending on what type of multimeter you have fireballs test should work
 
[ QUOTE ]
Some will recall that, whilst I was messing about with my alternator and charging regime, my rev counter failed.

It's failure coincided with removing the sensing lead from the alternator and extending it to sense at the domestic battery... all connections were made and unmade with the engine not running.

Many Thanks

Richard

[/ QUOTE ]

If something stops working always check the last thing that was done.
Sounds as though you've disturbed a connection somewhere, check the revcounter connection at the alternator (W) is clean and tight.
 
[ QUOTE ]
Most responses were that I must/may have disturbed a connection, but I have checked the connections in the vicinity, and remade them, and all seems OK, but the rev counter doesnt work so....

[/ QUOTE ]As a first step, why not bypass the existing wire by just getting a long bit of wire and connecting the rev counter directly to the alternator? That will tell you whether there's a fault somewhere in the original wire. You may need to check also that the rev counter is properly earthed.
 
[ QUOTE ]
As a first step, why not bypass the existing wire by just getting a long bit of wire and connecting the rev counter directly to the alternator? That will tell you whether there's a fault somewhere in the original wire. You may need to check also that the rev counter is properly earthed.

[/ QUOTE ]

I thought of this, but was concerned that the route from alternator to rev counter was through some gizmos which might alter the signal to suit the counter.

Volvo Penta MD22L
 
not generally - we put a rev counter on our Yanmar - its a standard counter - with the output off the altenator winding - same as you ...

the output of the alternator needs testing - either connect to a multimeter (the black probe goes to a battery negative somewhere) or as PVB suggested - a new cable straight to the rev counter. It should be all +ve but fluctuate a lot.

the earth test on the rev counter is just continuity between the neg connection of the rev counter and the battery negative!
 
[ QUOTE ]
I thought of this, but was concerned that the route from alternator to rev counter was through some gizmos which might alter the signal to suit the counter. Volvo Penta MD22L

[/ QUOTE ]No, it's a direct link from W terminal on alternator to W terminal on rev counter. Looks like there has to be a 12V positive feed to the rev counter as well.

You can check the wiring diagrams here on the Beneteau Owners Association website.
 
On outboards the rev counter is usually a DC driven device and a blown rectifier causes rev counter failure. Do you know if your rectifier drives the rev counter and have you tested the DC output?
Just crossing wires can blow a rectifier. Has your experiment caused a rectifier failure.
Be careful about sticking wires here and there to "test" items. It can multiply your problems.

I can't see why an inboard circuit would work differently to an outboard.
 
[ QUOTE ]
I can't see why an inboard circuit would work differently to an outboard.

[/ QUOTE ]Most inboard engines have an alternator, and the rev counter is driven by a connection to one of the alternator's AC windings. The frequency of this AC signal is directly proportional to the engine speed.
 
[ QUOTE ]
On outboards the rev counter is usually a DC driven device and a blown rectifier causes rev counter failure. Do you know if your rectifier drives the rev counter and have you tested the DC output?
Just crossing wires can blow a rectifier. Has your experiment caused a rectifier failure.
Be careful about sticking wires here and there to "test" items. It can multiply your problems.

I can't see why an inboard circuit would work differently to an outboard.

[/ QUOTE ]

Is the rectifier the same as the regulator? If not, I dont know what a rectifier is.

After my experiment, battery charging and engine starting remained exactly the same as before, so I dont think that anything has blown, but what do I know? /forums/images/graemlins/smile.gif

I'm just researching stuff at the moment, and cant start the engine in the marina at night, but may be able to have a go tomorrow.

My current plan is to test between the alternator rev counter output and earth, (alternator body), for DC Volts, (perhaps start at 600v and work down to 12, or whatever) - with the engine running.

Test for continuity between various points in the route from alternator output to rev counter.

Test for continuity between the rev counter -ve and battery negative, or some other point which is connected to battery -ve.

Cheers

Richard

Test for continuity between the
 
[ QUOTE ]
My current plan is to test between the alternator rev counter output and earth, (alternator body), for DC Volts, (perhaps start at 600v and work down to 12, or whatever) - with the engine running.

[/ QUOTE ]It's an AC output - set your meter to AC not DC.
 
[ QUOTE ]
[It's an AC output - set your meter to AC not DC.

[/ QUOTE ]

Will do - that's what I thought initially, and why I said what I was going to do /forums/images/graemlins/smile.gif

many Thanks
 
A battery stores DC current and your services work on DC, that's why they can run off the battery. If they are AC they need an inverter to run off the battery circuit.
The alternator creates AC current. The rectifier converts AC to DC.
Sometimes it's built-in to the Alternator and sometimes it's not. Rectifiers can also be part of the regulator mechanism.
 
[quoteNo, it's a direct link from W terminal on alternator to W terminal on rev counter. Looks like there has to be a 12V positive feed to the rev counter as well.

You can check the wiring diagrams here on the Beneteau Owners Association website.

[/ QUOTE ]

OK... I have the whole manual from the Moody Owners site and have seen the same wiring diagrams - I was confused because, in reality, the wire goes off down conduits, and appears at the rev counter and, on the wiring diagram, the wire goes into "13" on one diagram, and out of "13" on the other diagram..... I thought "13" was some kind of gizmo, but I guess it is just to help with continuity between the diagrams.

I think we're getting there...

Richard
 
[ QUOTE ]
Have you tried asking Halcyon ?

[/ QUOTE ]

I hadnt thought of it, and would guess that he will see my post and respond if he has anything to add.

If I get truly stuck, I'll give him a call.

Thanks for the thought

Richard
 
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