Alternator misbehaving

[BeckyJC]

Hi All,

 

Apologies in advance for my total lack of knowledge about boat mechanics, but.....

 

My batteries aren't charging properly, and I'm trying to figure out why. Cruising recently I had an issue where they weren't charging at all, and the engineer who came out to rescue me discovered a connecting wire that had come away from the alternator, and reconnected it. Afterwards, the batteries were charging fine for a few days (13-13.5 volts), then the "charging" voltage since has been around 12-12.5 volts. Without the engine running, my multimeter reads only about 11.6 - ick!

 

Normally, when I start the engine, the charge light comes on, and I have to rev the engine to kick-start the charging and make the light go out. Now, when I start the engine, the charge light flickers (whereas it was on constantly before) until I rev the engine, then it goes off as normal. The alternator does still seem to put some power out - I tried putting the boat in gear, as fast as it would go, and the voltage readout went up to about 12.6 volts - still charging a bit, but not as it should be. Also, I spotted a (tiny, but rather worrying and reoccurring) spark on the alternator itself (not on the connections).

 

I do have an adverc, but believe that even if this was faulty/dead the batteries should still charge from the alternator?

 

My ideas so far are:

Loose connection somewhere (nothing glaringly obvious, should I get the WD40 out and clean all the connections?)

Dodgy alternator

Find someone I can pay to come and sort it out, as electrics are kinda important and the spark has put me off running the engine until I get it sorted

 

Any ideas / pointers greatly appreciated, as I'm currently sitting in the dark to conserve power!

 

Thanks,

Becky

[Nickhlx]

Hi All,

 

Apologies in advance for my total lack of knowledge about boat mechanics, but.....

 

My batteries aren't charging properly, and I'm trying to figure out why. Cruising recently I had an issue where they weren't charging at all, and the engineer who came out to rescue me discovered a connecting wire that had come away from the alternator, and reconnected it. Afterwards, the batteries were charging fine for a few days (13-13.5 volts), then the "charging" voltage since has been around 12-12.5 volts. Without the engine running, my multimeter reads only about 11.6 - ick!

 

Normally, when I start the engine, the charge light comes on, and I have to rev the engine to kick-start the charging and make the light go out. Now, when I start the engine, the charge light flickers (whereas it was on constantly before) until I rev the engine, then it goes off as normal. The alternator does still seem to put some power out - I tried putting the boat in gear, as fast as it would go, and the voltage readout went up to about 12.6 volts - still charging a bit, but not as it should be. Also, I spotted a (tiny, but rather worrying and reoccurring) spark on the alternator itself (not on the connections).

 

I do have an adverc, but believe that even if this was faulty/dead the batteries should still charge from the alternator?

 

My ideas so far are:

Loose connection somewhere (nothing glaringly obvious, should I get the WD40 out and clean all the connections?)

Dodgy alternator

Find someone I can pay to come and sort it out, as electrics are kinda important and the spark has put me off running the engine until I get it sorted

 

Any ideas / pointers greatly appreciated, as I'm currently sitting in the dark to conserve power!

 

Thanks,

Becky

 

 

I am not sure about the internals of various alternators and which you have got / age etc but could it be that the brushes have worn down so much they are only making occasional contact ( and sparking when they do ) ?

 

One of the experts will be along soon...

 

Nick

Edited October 23, 2008 by Nickhlx

[BeckyJC]

I am not sure about the internals of various alternators and which you have got / age etc but could it be that the brushes have worn down so much they are only making occasional contact ( and sparking when they do ) ?

 

One of the experts will be along soon...

 

Nick

Hi, Cheers for the reply.

 

I have NO knowledge of what alternator I have, sadly. There are no markings / branding on it, but it has a bracket which obviously once connected it to something other than my boat, so I suspect it's not the one that was originally intended for my engine. Not much help I guess. My engine is an Isuzu 3 cylinder.

 

This could be a fun one to solve I fear Know any decent boat electricians in Sheffield, anyone?

 

Becky

[nbfiresprite]

Hi All,

 

Apologies in advance for my total lack of knowledge about boat mechanics, but.....

 

My batteries aren't charging properly, and I'm trying to figure out why. Cruising recently I had an issue where they weren't charging at all, and the engineer who came out to rescue me discovered a connecting wire that had come away from the alternator, and reconnected it. Afterwards, the batteries were charging fine for a few days (13-13.5 volts), then the "charging" voltage since has been around 12-12.5 volts. Without the engine running, my multimeter reads only about 11.6 - ick!

 

Normally, when I start the engine, the charge light comes on, and I have to rev the engine to kick-start the charging and make the light go out. Now, when I start the engine, the charge light flickers (whereas it was on constantly before) until I rev the engine, then it goes off as normal. The alternator does still seem to put some power out - I tried putting the boat in gear, as fast as it would go, and the voltage readout went up to about 12.6 volts - still charging a bit, but not as it should be. Also, I spotted a (tiny, but rather worrying and reoccurring) spark on the alternator itself (not on the connections).

 

I do have an adverc, but believe that even if this was faulty/dead the batteries should still charge from the alternator?

 

My ideas so far are:

Loose connection somewhere (nothing glaringly obvious, should I get the WD40 out and clean all the connections?)

Dodgy alternator

Find someone I can pay to come and sort it out, as electrics are kinda important and the spark has put me off running the engine until I get it sorted

 

Any ideas / pointers greatly appreciated, as I'm currently sitting in the dark to conserve power!

 

Thanks,

Becky

Bad News , This is the 1st sign of inpending failing of the rotor windings (Two or Three weeks before going totally dead). The alternator will need to be rewound. A good independent motor factor is best for the Job Cost around £45 pounds, Do a search under 'alternator repairs'. If your near the fens 'Taz Motors, Station Road, March' do a good quick job.

 

Firesprite

[BeckyJC]

Bad News , This is the 1st sign of inpending failing of the rotor windings (Two or Three weeks before going totally dead). The alternator will need to be rewound. A good independent motor factor is best for the Job Cost around £45 pounds, Do a search under 'alternator repairs'. If your near the fens 'Taz Motors, Station Road, March' do a good quick job.

 

Firesprite

Hmmm OK....cheers for the info. Not the news I wanted, but helpful all the same I have been told in the past that my alternator is on the small side for my battery bank anyway, so maybe I should cut my losses and replace the alternator altogether for a bigger one? Will research. Any idea how I can find out what alternators fit my engine?

 

Thanks.,

Becky

[alan_fincher]

I'm not sure it's been disclosed what type of alternator it is, (or did I miss that).

 

If looking at over £40 to rewind it, perversely it could cost less to replace it. I paid under £40 on e-bay for a 70 amp model suitable for our BMC, (no exchange required).

 

Obviously if it's something more expensive, it becomes more likwely that a repair will be a better prospect.

 

Any idea how I can find out what alternators fit my engine?

Cross posted with you, Becky.

 

If you tell people what the engine is, (or the model number of current alternator), then there is a good chance someone will know.

 

Sadly it will not be me, (unless you have a BMC!).

[Guest TerryL]

Hi All,

 

Apologies in advance for my total lack of knowledge about boat mechanics, but.....

 

My batteries aren't charging properly, and I'm trying to figure out why. Cruising recently I had an issue where they weren't charging at all, and the engineer who came out to rescue me discovered a connecting wire that had come away from the alternator, and reconnected it. Afterwards, the batteries were charging fine for a few days (13-13.5 volts), then the "charging" voltage since has been around 12-12.5 volts. Without the engine running, my multimeter reads only about 11.6 - ick!

 

Normally, when I start the engine, the charge light comes on, and I have to rev the engine to kick-start the charging and make the light go out. Now, when I start the engine, the charge light flickers (whereas it was on constantly before) until I rev the engine, then it goes off as normal. The alternator does still seem to put some power out - I tried putting the boat in gear, as fast as it would go, and the voltage readout went up to about 12.6 volts - still charging a bit, but not as it should be. Also, I spotted a (tiny, but rather worrying and reoccurring) spark on the alternator itself (not on the connections).

 

I do have an adverc, but believe that even if this was faulty/dead the batteries should still charge from the alternator?

 

My ideas so far are:

Loose connection somewhere (nothing glaringly obvious, should I get the WD40 out and clean all the connections?)

Dodgy alternator

Find someone I can pay to come and sort it out, as electrics are kinda important and the spark has put me off running the engine until I get it sorted

 

Any ideas / pointers greatly appreciated, as I'm currently sitting in the dark to conserve power!

 

Thanks,

Becky

 

Most likely it will just be the brushes sticking or worn. Remove the brushholder/regulator depending on the make and you will see two carbon brushes that are probably worn down. You can get them or a complete holder on eBay or a local electrical auto spares outlet but also check all the connections are clean and firmly attached.

[chris w]

Can you take a photo of the alternator and post it on here so we can identify it?

 

Chris

[Arnot]

My batteries aren't charging properly, and I'm trying to figure out why. Cruising recently I had an issue where they weren't charging at all, and the engineer who came out to rescue me discovered a connecting wire that had come away from the alternator, and reconnected it. Afterwards, the batteries were charging fine for a few days (13-13.5 volts), then the "charging" voltage since has been around 12-12.5 volts. Without the engine running, my multimeter reads only about 11.6 - ick!

 

Thanks,

Becky

Just a long shot but have you checked the fanbelt is tight enough?

 

Regards

 

Arnot

[BeckyJC]

Can you take a photo of the alternator and post it on here so we can identify it?

 

Chris

Hi All,

 

Thanks for all the suggestions. Further investigation this weekend has revealed a damaged alternator mounting bracket, causing the alternator to bounce around and short out on it's surroundings (hence the sparks...). It took a while to spot, as my alternator is mounted in a hard-to-get-to and hard-to-see place.

 

Sooooo I'm now trying to find out about mounting brackets. And how to replace them. And where to get one! So far online I have discovered (I think) that it is a dual-footed alternator with some sort of expanding bolt in the centre that its freely moving (but doesn't look like it should be!).

 

I will try and get pictures in the morning.

 

Any ideas?

 

Thanks again,

Becky

[chris w]

This is a not uncommon problem. Most alternators have a bracket at the bottom with typically an 80mm gap between them. The engine mount, on to which it bolts, is usually a few mm less than this so unless the gap is filled, the bracket will crack and break when the mounting bolt is tightened. Normally there is a small metal tube which slides through the alternator mounting bracket and takes up the excess gap. This is harder to explain than to see in practice.

 

Chris

[steelaway]

Hi Becky

 

Try typing 'alternator mounting' in google images. It shows variuse types

Here is one Clicky

[chris w]

I suspect that Becky may have been referring to the bottom bracket not the tensioning brackets.

 

Chris

[Sir Nibble]

Hi All,

 

 

Sooooo I'm now trying to find out about mounting brackets. And how to replace them. And where to get one!

Any ideas?

 

Thanks again,

Becky

www.woodauto.com

[Tony Brooks]

Hi All,

 

Thanks for all the suggestions. Further investigation this weekend has revealed a damaged alternator mounting bracket, causing the alternator to bounce around and short out on it's surroundings (hence the sparks...). It took a while to spot, as my alternator is mounted in a hard-to-get-to and hard-to-see place.

 

Sooooo I'm now trying to find out about mounting brackets. And how to replace them. And where to get one! So far online I have discovered (I think) that it is a dual-footed alternator with some sort of expanding bolt in the centre that its freely moving (but doesn't look like it should be!).

 

I will try and get pictures in the morning.

 

Any ideas?

 

Thanks again,

Becky

 

 

Becky

 

I assume that you are talking about one of the alloy brackets that are a part of the alternator.

 

As long as its not one of the Jap. made units it should not be too hard to get hold of a replacement bracket either new, form your local auto-electrical "overhauler" or an alternator form a scrap vehicle. However although changing most are not particularly difficult one may need to know what one is doing.

 

The drive (pulley) end bracket is normally easy but you will need a vice and probably a hammer an and brass drift. (or a puller)

 

The other end might involve soldering or undoing a few electrical connections. MY advice would be to take it off and deliver it to someone who does these things all the time - its far less likely to end in tears.