Thread: Do alternators die suddenly or they sometimes fade away?

As the brushes wear it will get to the point that the alternator is no longer supplying enough current so, yes they fade away. A blown diode would cause a sudden failure.
Regards,
Tote

Yes and yes and yes and yes. Brushes, diodes, regulators, wires etc can go partly or fully dead. Yours sounds like it's OK at the moment!

Not sure how easy one would be to fit re dash etc, but a volt meter is a good thing to have and cheap enough to buy and simple to wire in. Got a digital 24 volt and a digital 12 volt of evil bay for about $8 each posted.
Cheers Hall

My batteries are getting long in the tooth, about 5 years. I was disappointed with their performance running my Engel (turned out I was being unfair, it was hot in there and got 2 days off the aux).

Maybe alternators do not fade away often but batteries certainly do.

Batteries lose a % of their Amp hours every year and after 5 years I would be surprised if your batteries are not 30% down from new. I have a perfectly good 6 year old AGM under the house which I took out and replaced because it had lost capacity and didn't run the Engle long enough.
With alternators, the usual failure is a diode short circuit , and the red light comes on.It can happen that brushes wear to the point of not contacting , but also the red light will come on then usually at start up for a while. But I am pretty sure that alternators do not die slowly, unless a diode has gone open circuit and the alternator output is reduced considerably.
Having 13.7 volts at idle is not really a good indicator as a diode could be gone , but if the demand has been less than the output , the batteries could still be fully charged.

As hall says ,it is a good idea to have 2 volt meters, and you can tell what the batteries are doing and how the alternator is doing. I recall on mine on rough roads, I would show 14.2 which would suddenly drop to 13.1 regularly. Turned out to be a battery going open circuit on bumps, presumably because it had an internal crack in the conductor.
Regard sPhilip A

Originally Posted by JamesH

My batteries are getting long in the tooth, about 5 years. I was disappointed with their performance running my Engel (turned out I was being unfair, it was hot in there and got 2 days off the aux).

The only 'abnormal' thing here is that your batterys are perfectly OK after 5 years use.

Originally Posted by JamesH

Anyway I had cause to measure how well they keep charge. Seem to hold about 12.7/12.8 volts. Is that okay?

For a common or garden variety lead acid battery perfectly normal.

Originally Posted by JamesH

At idle, my original 1996 alternator pumps in 13.7 volts. Is that okay?

Again, perfectly normal for an alternator matched to common or garden variety lead acid batterys.

Originally Posted by JamesH

Dumb questions but I have no idea.

Only dumb if you don't ask.
Wish my batterys lasted this long.

Deano

Thanks everyone.

That was useful. I think Ill wait patiently for my batteries and alternator to clag themselves before replacing them. Will be going outback in July probably maybe before then I will have another think. Peace of mind purchase of new batteries is one thing but new alternator?

Incidentally, I have a very basic dual battery set up, some say too basic. Manual switch brings in second cranking battery otherwise everything runs off the first battery including all 12v plugs, so it kinda has a deep cycle life.


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James your memory is obviously better than mine.
Regards Philip A

You can buy a Scan gauge 2 from the US for between $100 or $200. It plugs into the diagnostics plug under the dash, OBDI or something.
It has been 6 or so years since I bought mine but you can set it to tell you all sorts of info including volts etc.
It works in real time & over the years it has been a very handy Peirce of kit. It attaches wherever suits you by velcro & can be moved from car to car (mine is in the 3rd) & it will save you chopping up your dash.
I have no interest in the company just like the little machine.
Try googling it.
Jonesfam