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Battery Warning light coming on as we move


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Our battery warning light has decided to start illuminating and buzzing as soon as we set off. The tachometer is also acting funny, and sometimes it just goes flat. 

I'm guessing I want to start looking at the alternator, alternator belt and batteries first?

 

The beeping and buzzing do go away for a while when we are plugged into shore power.  

 

Thanks

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In order, check any multiplug connectors from the engine then the belt tension then the rear connections on the engine alternator.

 

Multiplugs vibrate loose and get dirty contacts.

 

Most tachometers are connected to the engine alternator if there's more than one alternator, and a slipping belt can cause the symptoms you describe.

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It rather depends on the state of the batteries and the rpm, but with reasonably well charged batteries running at fast idle I would expect over 14volts. 12.2v doesn’t sound as though it’s charging at all. Try revving the engine a bit and rechecking. If the voltage doesn’t change, the alternator isn’t working. It is then a question of why isn’t it working!

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On 05/12/2020 at 13:14, canalboat77 said:

Our battery warning light has decided to start illuminating and buzzing as soon as we set off. The tachometer is also acting funny, and sometimes it just goes flat. 

I'm guessing I want to start looking at the alternator, alternator belt and batteries first?

 

The beeping and buzzing do go away for a while when we are plugged into shore power.  

 

Thanks

What engine is it?

.....bet its a Beta.

Multiplug on engine harness needs cleaning.

Happened quite a bit on our old Beta43. The rev counter stopping working was the sign of the plug connections failing.

 

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I am all but sure the brushes are mounted on the regulators. the top alternator regulator has a small wire coming out of it so I think that you either have/had an alternator controller or just possibly its battery sensed.

 

Undo the small screws securing the regulator to the body (probably on the one producing 12.2 volts) and lift the regulator out but remember the brushes hang down towards the centre axis of the machine and simply pulling the regulator off is likely to snap the brushes. You need to twist the regulator so a to lift the brushes so they clear the case.

 

Once the regulator is off take a torch and carefully inspect all the slip rings right the way round. The brushes can and do wear groves in them and I have known slip rings to wear right through so the brushes try to run on insulating plastic..

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1 hour ago, canalboat77 said:

Just as an update! We cleaned the multi-plug, and had to replace both alternators.

 

Thanks again. 

What was the problem with the alternators or were you just told they had to be replaced? Alternators at least £70 each, regulator and brushes about £25 each.

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1 hour ago, canalboat77 said:

Just as an update! We cleaned the multi-plug, and had to replace both alternators.

 

Thanks again. 

Both alternators!

If both have gone, does that not suggest there is something else wrong with the system? I can see how you can blow one up at a time, but both? If they both go then is there another bit of kit at fault?

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1 minute ago, Dr Bob said:

Both alternators!

If both have gone, does that not suggest there is something else wrong with the system? I can see how you can blow one up at a time, but both? If they both go then is there another bit of kit at fault?

That is why I asked what was wrong. I think one has a controller connected to it so if it was run at low speed for a period it MIGHT have burned out. However if it is brushes the both will have been running for the same time so could have worn at the same rate.

  • Greenie 1
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22 hours ago, ditchcrawler said:

If both alternators were commoned up, one could have failed a long time ago,

After fixing the issue, we realized what caused the alternators to both fail. 

 

We had an incident about two months ago where the sump pump for the engine oil shorted against the shared live feed connection point for both alternators. (I forget what the correct name is.) I've attached some pictures you can see the damaged caused. As you can see from the pictures one is with the pump on, and one is with it off. As the owner of the boat I should have moved where the pump was installed, as you can see it's on top of that power distribution point - so that's on me. It was installed there because that's where the brackets were. 

 

What we also realised was both alternators were supposed to be on separate line for each battery set (one for domestic, one for starter battery), and they weren't. 

 

 

 

 

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Edited by canalboat77
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1 hour ago, canalboat77 said:

 

 

What we also realised was both alternators were supposed to be on separate line for each battery set (one for domestic, one for starter battery), and they weren't. 

 

 

 

In that case one alternator could have failed years ago and only one was working

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