Is my alternator on the way out?

[Silebyman]

Long days boating all going well. Starting up after water top up ignition warning buzzer is cheeping. Rev counter is swinging a bit and one of the charging lights is flickering.

It's only happening at idle

Is the alternator stopping working?

It's an Izuzu 38 with twin alternators.

[KJT]

Do you have anything that might be drawing more current than the alternator is producing at idle?

Ours will do the same if, for example, we are running the washing machine, but the charge light goes out once the charge exceeds the current draw.

 

Ken

[Silebyman]

That might explain it. My wife spotted the fridge temp had been turned 'up' so made it work harder. Might have been about the same time as the noise started.

Maybe see if it's still doing it in the morning.

[Taslim]

Might be worth checking belt tension too.

[Silebyman]

As an update to this now we have got back from our trip.

 

We had it checked out at a boatyard as second opinion / peace of mind.

 

Their opinion was the alternator is still charging the batteries well, and was also supplying good voltage to the instrument panel.

 

We certainly didn't run into an flat battery problems, and the chirruping from the panel has got a lot better, but it's still there if you listen for it.

 

Any other ideas?

[Punk Stig]

you sure you don't have tinnitus?

 

Possible short somewhere on the ground wire?

[FORTUNATA]

Check warning lamp terminals and D+ wire is properly connected and terminals clean. Measure battery terminal voltage under load as opposed to offload with engine running.

That is, with stuff like fridges off or any other external load.

[bizzard]

If this chirruping is more noticeable at dawn and dusk a wee birdie could be nesting in there.

[Tony Brooks]

Once the alternator has energised a loose D+ terminal will not cause the revcounter to drop.

 

I had an identical question on the magazine forum yesterday and here is my reply:

 

If this happens a very few times a day and at long intervals I would check the alternator drive belt for tension in case an electric fridge or large inverter starting up puts such a load on the alternator the pulley slips in the belt. What we are finding increasingly with boats fitted with solar charging is that in sunny conditions and with long cruising days the solar voltage rises enough to cause the alternator's regulator to keep on shutting down for split second. This causes the warning buzzer to beep, sometimes the warning lamp to flash and as the rev-counter is driven from the alternator the rev-counter could start to drop. In this case it tends to be at short time intervals and turning an electrical load (not just one LED light) should stop it for a while. This depends upon the load being applied to the alternator that is doing this. It will probably be the engine alternator if you have two. If it is neither of these things then as the rev-counter and warning lamp/buzzer are affected I would suspect an internal alternator fault is developing but check all the connections on the alternator are tight, especially the blade ones. If you have a twin alternator setup it is probably not worth taking the alternator off for testing at this time but wait and sere how things develop. If one does fail just connect both battery bank positives with a heavy jump lead (take care not to create short circuits) after you make the first start of the day and remove it whenever you stop the engine. That will ensure the remaining alternator charge both batteries.

 

I think its a high solar voltage with fully charged batteries causing the alternator to shut down for a second or so. As I said putting a load on the relevant battery should stop it. If not then a slipping belt is more likely.

[Silebyman]

I'm a solar free boat - I know old school. I'm also 12v only apart from a mini inverter to power the cooker ignition.

 

I'm no longer getting the rev counter swing, and the instrument panel warning chirrup is nothing like as bad as it was, but annoyingly it's still there.

 

The problem only seems to occur ( or is noticeable ) at idle when queuing for locks, mooring etc.

[ditchcrawler]

I'm a solar free boat - I know old school. I'm also 12v only apart from a mini inverter to power the cooker ignition.

 

I'm no longer getting the rev counter swing, and the instrument panel warning chirrup is nothing like as bad as it was, but annoyingly it's still there.

 

The problem only seems to occur ( or is noticeable ) at idle when queuing for locks, mooring etc.

You are sure its not your oil pressure chirping

[Tony Brooks]

How often does it make this chirp? Can you tie it in with an electrical load being applied.

 

The dropping revcounter points to lack of alternator output but why we have no idea. Now the revcounter is steady the chirp could be oil pressure or overheat, in both cases I would be suspicious of the sender rather than a real fault. Try disconnecting each sender in turn (insulate the loose wire) and if the chirping stops you will have found the culprit.

 

Unless you have not given us a full report to what the boatyard told you I would be suspicious. They should give you numerical readings not general terms. A "good voltage" in their eyes could be 12V on charge (I have known this) but with well charged batteries that is far from a good voltage. You need 14V plus. Low charging voltages but still above (say) 12.5 with well charged batteries is more likely to indicate a blown diode than satisfactory alternator. To be sure you then need to check the charging current with significantly discharged batteries but at that time ignore the voltage, it will be low.

 

Have you checked and cleaned the multi-plug on the main wiring harness?

 

Now you say the revcounter is steady have you checked what Forrtunata said, in fact check all charging terminals and make sure the masters witches are OK.

 

There could well be a dry joint inside the alternator giving an intermittent fault once you eliminate everything else..

[Sea Dog]

and make sure the masters witches are OK.

 

 

Sod 'em! Proper naughty they are, changing all those nice men in Rupert trousers into frogs!

 

(Sorry to make light of such a helpful post )

[Just Heaven]

 

Have you checked and cleaned the multi-plug on the main wiring harness?

 

 

 

We also have an Isuzu 38 and had rev counter not working. Taking apart and cleaning the multi-plug on the RHS just below the fuel pump fixed it.

 

Steve

[Silebyman]

The multi plug was cable tied together by whoever installed the engine. Its probably worth a try pulling apart if it might help solve the problem

 

I was checking with a multi meter before I dropped into boatyard for a second opinion,

 

From memory I was seeing about 12.5-13 V into what were probably well charged batteries.

[Tony Brooks]

The multi plug was cable tied together by whoever installed the engine. Its probably worth a try pulling apart if it might help solve the problem

 

I was checking with a multi meter before I dropped into boatyard for a second opinion,

 

From memory I was seeing about 12.5-13 V into what were probably well charged batteries.

 

If they were well charged that is between 1 and 2 volts too low (assuming the meter is accurate). What was the current reading? This is important because at high currents the output voltage will be depressed but even then 12.5 would be very low.

 

Where did you take this measurement and was the engine revving well? Across the battery, in which case an undersized cable, bad connection or restive master switch could give low readings as could using a diode splitter - but not that low. Measuring at the alternator output terminal(s) will give a true reading. On idle the readings tell you very little.

 

Do not mess with the multi-plug untill you clarify excatly what you measured, where and what was the rough engine speed at the time.

 

I must say I find it odd that you did not tell us this in the original post. I also note that you have not replied to my question about how often it makes this chirp. It feels like trying to help with one hand behind your back and a blindfold on.

Edited August 18, 2016 by Tony Brooks

[Silebyman]

Apologies for not making this clear at the start - I was using my phone on the towpath whilst concerned my holiday was about to go down the toilet..

 

I'm now back at work so I can think more clearly, but taking current readings is not possible

 

As I previously mentioned the chirrup only occurs at idle - at normal engine speed it goes away.

 

I, and the boatyard took readings using my multimeter from the alternator terminal. I can't calibrate the multimeters accuracy, but I've no reason to suspect it's any worse that any other.

 

Idle speed is about 800rpm, possibly 850, and it chirrups more that once a second. Perhaps 2-4 times a second. It's hard to count.

 

The crank's rotating approx. 13 times per second, or if you consider firing cycles at 6,5 times per second are both too fast. If alternator ratio is then perhaps 3:1 it can't be chirruping once per alternator rev as it would be doing it 39 times per second which would probably be too fast for a human ear to pick up...

[Flyboy]

We also have an Isuzu 38 and had rev counter not working. Taking apart and cleaning the multi-plug on the RHS just below the fuel pump fixed it.

 

Steve

 

This 'chirping' problem has come up before on Isuzu, Beta & Barrus engines. They all have a similar multi-plug on the harness. Pulling it apart and cleaning it with switch cleaner or WD40 has cured the problem in most cases.

[Tony Brooks]

Apologies for not making this clear at the start - I was using my phone on the towpath whilst concerned my holiday was about to go down the toilet..

 

I'm now back at work so I can think more clearly, but taking current readings is not possible

 

As I previously mentioned the chirrup only occurs at idle - at normal engine speed it goes away.

 

I, and the boatyard took readings using my multimeter from the alternator terminal. I can't calibrate the multimeters accuracy, but I've no reason to suspect it's any worse that any other.

 

Idle speed is about 800rpm, possibly 850, and it chirrups more that once a second. Perhaps 2-4 times a second. It's hard to count.

 

The crank's rotating approx. 13 times per second, or if you consider firing cycles at 6,5 times per second are both too fast. If alternator ratio is then perhaps 3:1 it can't be chirruping once per alternator rev as it would be doing it 39 times per second which would probably be too fast for a human ear to pick up...

 

It could be fully charged batteries causing the regulator to "hunt" and if so I feel it is very rare. I would welcome SirN's input on this. If that is the case putting a reasonable load on the battery and thus alternator should stop it immediately.

 

However that leaves the 12.5 to 13 volt question unanswered. f these readings are accurate, at the back of the alternator, and with the engine revving it points to a faulty alternator, possibly a dry solder joint or some such.

[Sir Nibble]

Sounds like a possible intermittent brush contact. Slacken the belt and rotate the alternator slowly by hand with ignition on and watch the warning lamp. Difficult to venture much of an opinion without knowing what alternator it is, it is probably a 3rd generation 6 diode machine but might be a battery excited model. Picture?

[Silebyman]

Sorry for break in communications other things have been taking priority...

 

It's an A127 type 90a unit made by prestolite I think.

 

Could it be a regulator problem? If so I could replace it, but having hunted around all the regulators I can find seem to state 70a max

 

As an aside I seem to be constantly tensioning the alternator belt. I seem to recall reading somewhere that 70a is about the limit for what an SPA belt can manage with.

 

Would I be better off replacing with a lower amperage unit?

[Tony Brooks]

90 amps may well be OK on a single belt, especially if you by a quality one like Gates. I do not see how the voltage regulator can be rated for current. I just think the vanilla A127 have a maximum of 70 amps output. The rotor just might have a slightly lower resistance and hence allow a slightly greater current flow through the regulator but we are probably only talking a fraction of an amp.

[tillergirl]

Annoyingly we have an alternator light flash at idle. Someone told us it was mkre than likely the sterling alternator regulator causing it. SO the question is , is there any point in having the regulator if its not working correctly?

[Tony Brooks]

<Echo on>

 

I find that diagnosis suspect.

 

A short while ago Sir N said it could be worn alternator brushes so take the alternator belt off and try turning the pulley by hand with the ignition turned on. If the light flashes brushes or slip ring problems are the most likely faults.

 

You can disable the Sterling by disconnecting the fly-lead that pokes out from the back f the alternate or if the Sterling has a multi-plug on it disconnecting that when everything is turned off. If the problem goes away whne you run the engine its the Sterling so you may as will disconnect it.