Couple of alternator questions
Hi, all,
The current alternator in my '88 4WD Van is an AC Delco, installed in 2015 when my original Denso unit finally quit (after replacing seals in the PS pump so it didn't drip any more, and cleaning the alternator and replacing the brushes). It has started to whistle lately, and while it's still putting out 14.3V+ I don't know how much longer it will last, and I'd like to rebuild my Denso to replace it. The brushes in the Denso are still fine, but I think the diode may be bad and I'd like to buy a new Denso diode block to put in it. I've read many of the alternator threads that mention the diodes but other than the recommendation to pick them up at the pick-and-pull I haven't found a part number or source for a new Denso diode block.
Is it possible to buy a new Denso diode block?
I'd be interested in any insights as to the cause of the whistle. I've read in other places that it can indicate the alternator is working too hard. The battery is fairly new (within the last two years) and the whistle is there even when the battery has been fully charged with an AC charger. It goes up in pitch as the RPM goes up, not in a narrow range of RPM like a resonant vibration frequency.
One thing that started about the same time as the whistle was that the charge light came on. It now only comes on when the van is idling just after a start from cold, and it goes off once the engine is revved above about 1000 rpm the first time. Looking at battery voltage at the same time, when the charge light is on right after the cold start the voltage at the battery terminals is 12.0-12.3 or so, when revved the voltage goes up, eventually reaching 14.3V+, and dropping back into the 13s when allowed to go back to idle.
Thanks,
John