Whine->Dead car(electrical)

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My 07 MDX has whined for a day or so with RPM. Today within a 5 min span every nanny and light(stability, abs,air bag, Awd) turned then it barely moved. Finally battery and brake red lights on as it felt to be stalling. It would not restart and once jumped not run without jumpers. I limped coasted into small auto repair shop.

I presume alternator is in need of replacement. Is the battery junk too?
 
Alternator is the likely culprit. I would stress test the battery to be sure it also doesn't need replacement. Sometimes a weak battery can kill the alternator.

What's the mileage?
 
Load test the battery which may involve charging it to full capacity first.
The part store will be glad to do it for you by bringing it to them unless you have a load tester.

If battery is good, then test the alternator.
 
Just a quick question to make sure I wasn't getting jerked around, does the battery have to be in good shape before you can test the alternator?
 
Battery is 3 years old. No DIY here, car is 50 miles away at small repair shop thankfully near commuter rail. Hopefully good sign three people in professional dress walked across parking lot to pick up cars from rail.
 
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At the mileage you have I would say the Alternator is toast most likely.

If you can afford it replace the battery as well. Batteries typically last 5 years most of the time and 3 years is getting on in age so it has probably lost some capacity already and will demand more of your alternator. If you can't afford to replace it then have it load tested at the bare minimum to make sure it is well enough not to add additional strain on the alternator. Especially in Honda/Acura vehicles where they undersized the batteries for weight reduction. (for my liking anyway)

Modern cars can be really fussy about proper battery voltage and a bad alternator or weak battery can wreak havoc on some vehicle ECM's and other control modules.
 
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Just one day of whining and zero indication on the dash that alternator was not charging before leaving you stranded? I would expect, battery light to come on for about half an hour of driving before stalling on you.

Try to ask the shop if they can get an OEM quality rebuilt Denso. Most other store brands are NOT recommended. Otherwise, at least get your original core. If you are handy, you might be able to swap the brushes/diode pack and get another 100K out of that alternator. Since it was whining and not making any mechanical noises, the chances are bearings are still good. You will have to source the brushes/diode pack on the internet but replacing them would be trivial.
 
I and others I know have had electrical problems. Tried changing the alternator and in the end we all had to change battery too. Someone explained why to me and it made sense. Don't remember why now. I just know I have seen it happen over and over.
 
LIkely the battery was weak, keeping the alternator at high load, getting it hot and whining.

When the alternator quit, the weak battery barely ran the car 1 minute.
 
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