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Rev counter stopped suddenly


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Is the "fan" belt still present, tight, and the alternator spinning at full speed?

 

As Chris says, if it is electronic, it is usually driven by a connection to the alternator, but if that has fallen off completely or broken, I'm not convinced the needle would move at all on starting.


Flat battery?

 

You wouldn't be able to start the engine if there was, would you?

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If the engine alternator is working ok & all connections are sound, I suggest you check the plug/socket in the main harness that goes to the instrument panel also the plug on the back of the rev counter. Take them apart & spray with switch cleaner or WD 40.

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The rev counter on my Barrus Shire has suddenly stopped working. The needle moves very slightly on starting up then drops back to its rest position. Any suggestions welcome....

My rev counter does this occasionally (maybe once every six month), i solve the problem with a few taps on the glass and it starts working again... ive put it down to a bad connection but havent investigated yet.

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Would this affect charging at all, as my rev counter stopped working last time we were out and have now noticed that ammeter doesn't move at all whilst engine is running but battery light does go out.

 

I think that is a symptom of failed main positive diodes. The field diode output would extinguish the warning lamp but there would be no output.

 

Good practice says check the multi-way plug on the main harness and the W connection before taking the alternator off for testing.

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My rev counter does this occasionally (maybe once every six month), i solve the problem with a few taps on the glass and it starts working again... ive put it down to a bad connection but havent investigated yet.

 

 

Mine on rare occasions has done this too . I see the needle drop back , my inbuilt negativity kicks in and i mutter a few obscenities .

Following some sort of " instinct of the desperate " i tap the screen a few times and the needle springs back to life . Its happened maybe 3 times in the 4 years ive had the boat .

Not much help maybe , but who knows maybe the problem for the OP will self fix itself too before the wires need playing with ?

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I think that is a symptom of failed main positive diodes. The field diode output would extinguish the warning lamp but there would be no output.

 

Good practice says check the multi-way plug on the main harness and the W connection before taking the alternator off for testing.

 

 

 

 

Cheers tony, will have a proper look when it warms up a bit. We are on a landline at the minute so charging is not an issue.

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You could try it with the Shorepower Charger turned off,the Alternator might be shutting down straight away as the Battery Voltage is already up

 

CT

The alternator regulator has nothing to do with the tacho signal as it comes directly from the coil pack/diodes.

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Mine on rare occasions has done this too . I see the needle drop back , my inbuilt negativity kicks in and i mutter a few obscenities .

Following some sort of " instinct of the desperate " i tap the screen a few times and the needle springs back to life . Its happened maybe 3 times in the 4 years ive had the boat .

Not much help maybe , but who knows maybe the problem for the OP will self fix itself too before the wires need playing with ?

That sounds like a duff connection on the back of the meter. I've had that happen a couple of times on different boats. On one, the problem wasn't the lead to terminal connection, but that the terminal itself was slightly loose. Taking all the leads off and tightening the nut that holds the terminal to the body of the meter sorted it.

 

Another symptom of that can be the counter suddenly over-registering as if the engine was racing, except that you can hear that it's not. The bad conn puts extra peaks and troughs in the signal, confusing the electronics that work by counting the peaks in the sine wave coming from the W terminal.

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The alternator regulator has nothing to do with the tacho signal as it comes directly from the coil pack/diodes.

 

If the regulator shuts down the field/rotor current completely then no voltage gets induced in the main coils and therefore no tacho signal. Mostly leakage through the alternator and/or residual permanent magnetism in the rotor is enough to generate a usable signal, but I have seen it more than once where the tacho stops working when the batteries are charged and there's enough solar to handle the running load.

 

MP.

  • Greenie 1
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That sounds like a duff connection on the back of the meter. I've had that happen a couple of times on different boats. On one, the problem wasn't the lead to terminal connection, but that the terminal itself was slightly loose. Taking all the leads off and tightening the nut that holds the terminal to the body of the meter sorted it.

 

Another symptom of that can be the counter suddenly over-registering as if the engine was racing, except that you can hear that it's not. The bad conn puts extra peaks and troughs in the signal, confusing the electronics that work by counting the peaks in the sine wave coming from the W terminal.

 

Cheers

 

I fall very much into the " if it aint broke ...... " camp when it comes to this sort of thing . Very neatly , this mentality coincides with a tendancy towards idleness !

This is based on the fact that each time its happened it has fixed itself almost immediately . Having read Bizzards post above it has reminded me that its always happened in winter & though mines a trad stern the engine room at the back does get a bit of condensation so maybe theres a link .

 

However , I do always read threads such as these so that if / when the fault develops into a problem i have at least some awareness of where the fault may be .

So thanks again for the above advice

 

cheers

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If you read MP's post again, the 2nd. sentence seems to contradict the 1st.

It would if it didn't start with "Mostly". It doesn't always happen that when the regulator shuts down charging the tacho loses signal, but it can happen with some alternators and I've experienced it myself.

 

MP.

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Had this with my Barrus a number of times each time it was the block connector at the back of the gauges.

 

It appears that the weight of the cable pulls down on the connectors so I fixed it so that the Weight of the cable is held up by the judicious use of a couple of cable ties. Problem hasn't occurred again since I did thus.

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If the engine alternator is working ok & all connections are sound, I suggest you check the plug/socket in the main harness that goes to the instrument panel also the plug on the back of the rev counter. Take them apart & spray with switch cleaner or WD 40.

If the engine alternator is working ok & all connections are sound, I suggest you check the plug/socket in the main harness that goes to the instrument panel also the plug on the back of the rev counter. Take them apart & spray with switch cleaner or WD 40.

Based on the replies so far I think I'll try this as a starting point. Thanks all. I'll keep you posted.

Might even try it twice ...doh!

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Just to add to my previous post I noticed that because of the way the harness is put together and the block connectors are lead to the relevant areas it appears to me that their is slightly more pull on the block connector that goes to the rev counter gauge, so getting them firmly in place and taking the weight off them should help prevent this in future.

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If the engine alternator is working ok & all connections are sound, I suggest you check the plug/socket in the main harness that goes to the instrument panel also the plug on the back of the rev counter. Take them apart & spray with switch cleaner or WD 40.

Never use WD40 on electrical circuits. It is conductive and highly flammable, it also eats plastic.

Always have a can of switch cleaner handy, I'm sure Maplins must sell it.

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