Alternator?

[Guest]

During yesterday's cruise the alarm and battery light came on for about 10-15 seconds, this happened around a dozen times, as you can see in the photo the volt metre does not drop when this happens (the bottom left dial is oil pressure which is fine)...I am thinking alternator or maybe a relay but my electrical knowledge is limited, anyone have any thoughts please.

[JanetAnne]

Voltmeter shows battery condition rather than charge rate so would not be affected by the alternator pulsing on and off.

Chances are the control box in the alternator itself (or its external counterpart should one be fitted) is on the way out. Brushes are a possibility but rarely fail before the control box.

 

[Meantime]

Sounds like worn brushes or faulty regulator. On a lot of alternators they all form one pack held on by a couple of screws.

Generally speaking the battery light is supplied with 12V from your battery and connected to the alternator. When the alternator is not running that connection is effectively at 0V and therefore the bulb, and or buzzer will sound. When the alternator is giving an output the voltage will rise and the voltage will be the same on both sides of the bulb or buzzer and therefore it goes out. So the fact that the bulb comes on means that for that period of time the alternator is not giving a charge. 

As JA said, the voltmeter will tell you the state of the batteries.

[annv]

Hi ignition light comes on when there is no charge coming from armature this can be brushes worn/sticking, control box or what is most likely LOOSE/corroded wire connections,especially on a boat, people will just crimp wire onto connectors without greasing bare wire first,laziness, check all connections clean with emery paper remake cropped joints first dipping in vaseline if this doesn't cure the problem and if you have a alternator with a cassette this contains the brushes and control box held on with two screws on rear end of alternator at the rear of alternator can be changed without removing unit just undo the two screws and lift out unit by tipping down and out and replace, much much cheaper than exchange unit, just go on line or go to motor factors with make and model of alternator and look for brush cassette,. John

[Guest]

Thanks guys, been cruising an hour today and so far it hasn't done it.

[Meantime]

My advice would be to check the brushes as a matter of urgency. Once they start to play up it is not normally long before they fail permanently. The same with regulators, but they tend to be more affected by heat, so less likely this time of year.

Can you take a picture of the back of the alternator? Do you have a make and model number?

[Guest]

[Meantime]

I don't recognise the make or model of the alternator, but you will need to remove the black cover to get to the brushes and regulator.

The plus and negative wires are straight forward. It appears there is a thinner Brown wire under the positive terminal, this will feed the regulator and appears to go under the plastic cover.

The W terminal is the tacho pulse and will go to your rev counter. 

The two wires on the other terminal will more than likely be your battery lamp and buzzer. They will both be fed by 12V from your ignition switch and the earth side of them will be connected to that terminal on the alternator. When the alternator is not spinning or providing an output then that terminal will be at zero volts and the lamp and buzzer will be on. As the alternator spins and an output is generated the voltage on that terminal will rise to 12V and therefore both sides of the lamp and buzzer will be at 12V and therefore the lamp will go out and the buzzer will stop.

Whilst the wiring could do with some attention, if the lamp is coming on whilst the engine is running the voltage on that terminal must be dropping to zero indicating that the alternator has stopped producing an output. Since the battery lamp earths through the alternator when there is no output you can rule out faulty connections on the battery lamp terminal and negative terminal. A faulty connection on the W terminal would make the rev counter jump. A faulty connection on the positive terminal shouldn't stop the alternator output as most alternators are "self exciting" once they have started running. Long and short of it, is that the wiring or connections are unlikely to be the cause of your problem.

 

[Smoggy]

Looks like a valeo, I may have one in my shed but would be micro vee so pulley would need swapping.

[Guest]

Thanks for the info guys, there is no rev counter but the speedometer needles drops to zero when the event occurs..

[Meantime]

18 minutes ago, Smoggy said:

Looks like a valeo, I may have one in my shed but would be micro vee so pulley would need swapping.

Yes, the position of the terminals look about right. The picture shows the alternator with the black plastic cover removed. The brushes and regulator pack are situated between the main positive and negative terminals.

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[annv]

Hi it looks like a Marelli alternator French crap throw use it as a mud weight also your connections look very corroded i would advise you to rectify them or at last soak then in penetrating oil,  otherwise if its working now !!!!  John

[gancanny]

not worth the trouble,  get a new one,  PANKS in norwich are the people,  then you will have peace of mind instead of having a niggling doubt about the one thats on and not performing

[WherryNice]

2 hours ago, Jemaki said:

Thanks for the info guys, there is no rev counter but the speedometer needles drops to zero when the event occurs..

You do have a rev counter, it's the big one in your pic that I think you might be calling the speedometer? Unless I have missed somthing, in which case......

[Guest]

10 minutes ago, WherryNice said:

You do have a rev counter, it's the big one in your pic that I think you might be calling the speedometer? Unless I have missed somthing, in which case......

Yes I was having a blonde moment 

[ExSurveyor]

I had the same problem, switching a cabin light on stopped it. Changed the alternator and it did it less but still did occasionally. I have noticed after lockdown the rev counter is not working, something to look into later.

[Guest]

15 minutes ago, psychicsurveyor said:

I had the same problem, switching a cabin light on stopped it.

Next time I'm cruising can you switch the cabin light on, I'll let you know if it works... 😉

[ExSurveyor]

I could have switched a light on the other day when you went past but didn't realize you had a problem

[Smoggy]

If this is any use to you let me know before 12.00 tomorrow and I'll bring it to the boat with me, I'll be at surlingham ferryhouse most of the weekend.

There's no W terminal but the green and yellow wire is the same as I had to fit a phase tap for tacho, it was working ok when removed, originally off peugeot xud9 engine.

[ZimbiIV]

Just a thought but check the timing belt is okay first and not slipping. If its that water is not circulating either that is terminal!.

paul

[Guest]

First of all a thank you for all the input and suggestions from you guy's.

Just a follow up.....this morning when I tried to start the engine it turned over but would not fire up, it normally goes on the first half turn and is as sweet as a nut, we have breakdown cover so called a mechanic, when I explained the symptoms with the engine light and buzzer etc, the first place he went was under the dash and lo and behold a pin inside the ignition loom had come adrift and had pushed inside itself. Once repaired everything was as right as rain, a heads up to Old Berkshire Boy who PM'd me and suggested I check under the dash and the wiring looms 😉 Once again thanks all 👍 

John.

[OldBerkshireBoy]

👍