Alternator overcharging

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Ian_Rob

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I have been getting an intermittent warning signal from my electrical panel. It has happened perhaps 4 times in three years - the last time 2 weeks ago. The diagnosis is that the alternator is overcharging, delivering 15v and it needs to be removed and checked (and probably a diode replaced)?

If it is delivering 15v, will leaving a few lights (in addition to the fridge and chart plotter) be sufficient to limit any battery damage until I can get it fixed. If it is diode, is it a DIY job?
 
Ian_Rob said:
I have been getting an intermittent warning signal from my electrical panel. It has happened perhaps 4 times in three years - the last time 2 weeks ago. The diagnosis is that the alternator is overcharging, delivering 15v and it needs to be removed and checked (and probably a diode replaced)?

If it is delivering 15v, will leaving a few lights (in addition to the fridge and chart plotter) be sufficient to limit any battery damage until I can get it fixed. If it is diode, is it a DIY job?
Click to expand...

Diode will normally give you a low charge current, not high voltage, sounds more like a intermittent connection and the regulator is getting a false voltage and turning off.

Brian
 
Thanks Brian

One article I have just read says that the alternator should give 14.2v max whilst another says 14.8v so 15v sounds a little high but perhaps within the upper limit?. I need to check it for myself. I am sure it is impossible for you to say but is it likely that this intermittent connection is a fault within the the alternator itself or in the wiring from the alternator or perhaps even a problem with the regulator?
 
VicS said:
I agree with that, but check all connections first.
Click to expand...

Apparently Volvo don't supply the regulator as a separate item so if there is still an issue after checking the connections, I'll speak to the manufacturers of the alternator and hopefully source a suitable replacement through them.

Thanks for the guidance.
 
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Ian_Rob said:
Apparently Volvo don't supply the regulator as a separate item so if there is still an issue after checking the connections, I'll speak to the manufacturers of the alternator and hopefully source a suitable replacement through them.

Thanks for the guidance.
Click to expand...

Or take it to an automobile electrician. They will be able to fit a new regulator unless there is genuinely not one available for that particular alternator.

I was lucky when I had the same fault on a car alternator a few years ago.
We had a "motoring section" of our works sports and social club. A request to one of the engineers who ran the motoring section first thing in the morning had spares delivered from a local factor before lunchtime. So one could drive to work with a dodgy motor but have it fixed by the end of lunch hour.
 
If you go to http://www.marinepartseurope.com/en/default.aspx?gclid=CP6-9piRqLcCFYuR3godPHcAdQ and search for your engine, it will give you the part number of the alternator. Put this into google and it will direct you to sites selling the alternator. This will give you the maker and model number of your alternatorm which you can use to source a new regulator. I did this and picked up a new regulator for about £30 on ebay.

The alternators are standard items, not marine ones at all. The only real thing about them is that they are battery sensed, so that they deliver current based directly on the state of charge of the domestic battery rather than sensing the voltage emerging from the alternator.

Before all that, do check the wiring is intact!
 
I would suggest OP gets digital volt meter and connects semi permanently to the battery. If it is just an intermittent warning then it may be the warning system at fault not the alternator. Monitor the voltage under motoring conditions and especially if the warning operates.
A regulator can occasionally fail in short circuit mode such that alternator runs at full power. Voltage will be higher than 15volts. Batteries will boil; and overheat and light bulbs and other devices will fail. This happened to my son's little Toyota car. it tends to happen permanently not intermittently. There is not doubt even without a warning system.
As said a loss of sensing wire in battery sensed systems can be intermittent and give similar outcomes. good luck olewill
 
Thanks for the responses. I'll monitor it as suggested. Hopefully its is just a connection issue. The alternator (which is made by Mitsubushi) has an internal regulator so would have to be taken apart.
 
As a guide
Volvo MD 2020d
Broke a stud on my volvo alternator recently. It was corroded & i wanted to fit an hour meter
I took the alternator to a refurb place in danbury essex.
It turned out that bearings were on the blink & something else ( would it be brushes?) plus regulator needed changing
Whole lot cost £110-00 for complete refurb
They also changed all the studs so if i have any broken wires etc i can replace without shearing them off as before
Regulator was not from volvo. They did tell me name of alternator manufacturer, the chap recognised it straight away, but as it means nothing to me i have forgot name but it was not Mitsubishi,
 
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Maybe not exactly the same problem but a few years ago my Sterling regulator was occasionally cutting out and displaying a high voltage alarm. I was advised that the cause was a faulty earth connection. Despite checking every connection I could find I could not locate a problem and the fault occurred several more times. About two years later I fitted a digital volt/amp meter, during which I found another earth connection, from the alternator to the engine block. Renewing this has cured the fault permanently.
 
Daydream believer said:
As a guide
Volvo MD 2020d
Broke a stud on my volvo alternator recently. It was corroded & i wanted to fit an hour meter
I took the alternator to a refurb place in danbury essex.
It turned out that bearings were on the blink & something else ( would it be brushes?) plus regulator needed changing
Whole lot cost £110-00 for complete refurb
They also changed all the studs so if i have any broken wires etc i can replace without shearing them off as before
Regulator was not from volvo. They did tell me name of alternator manufacturer, the chap recognised it straight away, but as it means nothing to me i have forgot name but it was not Mitsubishi,
Click to expand...

A Valeo alternator perhaps?
 
I purchased a spare starter motor and spare alternator from http://www.startermotor-alternator.co.uk/marine_parts.php

I was able to get the correct part numbers from my service manual, but they have them listed by engine, by engine manufacturer spares number, and by original manufacture part number.

I had very fast response to emails, and very fast delivery - An easy and reasonably priced company to deal with - they get my recommend.
 
Oddly enough I have exactly the same problem with my Volvo MD 2030B. An intermittent chirp from the alarm always when the engine is idling but only two or three times a year. This happened both before and after I replaced the alternator _ I reckon the chap I took the first alternator to bu55ered it up in testing so I had to buy a new one.

Anjyway the probloem has now developed a little further with two cases of the alarm bleeping, the rev counter dropping to zero and the leccy warning light coming on only for the system to revert to normal after maybe 5 seconds. That has happened twice now.

I thought it might be the sterling charger but the two lates issues have occurred without the sterling in circuit.
 
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