Intermittent alternator charge

[Jonty]

Hi all I?ve posted on a FB page on this issue but not having much luck. My almost new Dgo alternator is randomly stopping charging on occasion when I am idleing only. As soon as I give it a kick of revs it starts to charge again and always charges when I?m driving and not idling. My battery light comes on when I turn the key and never comes on when the alternator stops charging. I thought I might have an issue with the exciter but my understanding is that once excited the alternator should stay charging so that doesn?t explain why the issue is intermittent. Also odd that it always charges when driving and the issue is only at idle. Any ideas?

[Bitsyncmaster]

I assume you see the volt gauge drop at idle. What voltage do you see then?

[Jonty]

I assume you see the volt gauge drop at idle. What voltage do you see then?

Yes it drops to 11.5v. When it decides to charge again it immediately shoots up to 13.5v. I’m a bit confused how an alternator can stop charging then start again. If I turn the car off and start it again it starts charging agsin.

[Bitsyncmaster]

Yes it drops to 11.5v. When it decides to charge again it immediately shoots up to 13.5v. I?m a bit confused how an alternator can stop charging then start again. If I turn the car off and start it again it starts charging agsin.

So it does charge at idle but then stops after high RPM dropping back to idle? If it never charged at idle I would guess it's just the alternator does not turn fast enough at idle speed.

[Jonty]

So it does charge at idle but then stops after high RPM dropping back to idle? If it never charged at idle I would guess it's just the alternator does not turn fast enough at idle speed.

No it charges at idle then randomly stops charging. If it sits idleing it sometimes just starts charging all on its own or if I step on the gas it starts charging again.

[Jonty]

No it charges at idle then randomly stops charging. If it sits idleing it sometimes just starts charging all on its own or if I step on the gas it starts charging again.

Also just confirming I?m getting 11.8v on the brown/yellow wire at all times.

[Bitsyncmaster]

No it charges at idle then randomly stops charging. If it sits idleing it sometimes just starts charging all on its own or if I step on the gas it starts charging again.

Well something is intermittent. So verify all wire connections on the alternator are tight. Remove and install the bulkhead connectors. Maybe try adding a ground wire on the alternator housing. If all that still shows the problem, my guess would be the new alternator has the problem internally.

[Michael]

First thing is verify it's not the gauge. Put a multimeter on it and see what the alternator is doing at the alternator and the battery. That gauge is crap, don't trust it.

[David T]

What you are seeing is not "intermittent". It is ALWAYS doing the same thing under the same conditions. When the RPM's of the alternator drops to idle it cannot charge because it is going too slowly. In fact, it is normal. During idle an alternator cannot put out it's full rated output so the battery carries some of the electrical load. If you have any concerns go to an auto store and they will test your alternator and battery for free. My guess is your battery is undercharged or it needs to be replaced, especially if it is over 5 years old.

[WHO1DMC]

Myself I would check the voltage at the battery and alternator with a in car battery load tester or multimeter. See what differences you get. If you question if the battery or alternator have a problem take them somewhere to be tested. Now if there fine then the cables might be bad they don't last forever. I replaced my cables and I did the full ground and power upgrade and gained 1 to 2 volts to the car. So if any car of this age are running with there original battery cables they should be replaced or your just asking for electrical gremlins to plague you.



Dave B.