99 accord - alternator or regulator?

My 99 Accord V6 has and electrical problem at idle speed. Headlights, wipers, interior lights - everything dims or slows down when the car is idling. When the engine revs just a little, everything returns to
normal. There's also a little bit of a whine I can hear while the problem is happening.
The battery did test low and due to its age it probably needed replacing. So I replaced it. But low-rpm voltage is still low. The problem still exists.
I've got my eye on replacing the alternator, but I understand there's also a voltage regulator part that tells the alternator when/how much/if to charge.
How can I figure out what the problem is without throwing darts with my money?
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If I'm not mistaken the regulator is internal on your alternator. In any event, the symptoms are consistent with a bad alternator.
The real tests are done with a digital voltmeter across the battery. The DC voltage should be between 13 and 16 volts (low part of the range in hot under-hood temperatures, high part of the range when cold). The voltage should not change significantly when the engine is revved from idle. The AC voltage should be under 0.1 VAC.
If the voltage is above 16 volts, the regulator is bad. If the voltage is low at idle but comes up to spec when the engine is revved a bit, that is a bad sign for the alternator. If the AC voltage is just above 0.1 volts, the battery is not in good shape (your new battery should not show much AC voltage at all unless the alternator is bad). If the AC voltage is more like 0.5 volts or more, you can be certain you have bad diodes in the alternator.
My prediction - you will have the low voltage coming up to normal as you rev the engine, and high AC voltage across the battery... a definite bad alternator. Anyway, that's what the whine leads me to suspect.
Beware of aftermarket alternators - they have earned a bad reputation for reliability.
Mike
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Before you spend all your money- Check the grounds. The symptoms you describe could be from bad grounding.
-Pete
Me wrote:

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On 2005-03-27 snipped-for-privacy@nowhere.net said: >Newsgroups: rec.autos.makers.honda,alt.autos.honda >My 99 Accord V6 has and electrical problem at idle speed. >Headlights, wipers, interior lights - everything dims or slows down >when the car is idling. When the engine revs just a little, >everything returns to normal. There's also a little bit of a whine >I can hear while the problem is happening. >The battery did test low and due to its age it probably needed >replacing. So I replaced it. But low-rpm voltage is still low. The >problem still exists. >I've got my eye on replacing the alternator, but I understand >there's also a voltage regulator part that tells the alternator >when/how much/if to charge. >How can I figure out what the problem is without throwing darts >with my money? Are you sure the alternator drive belt isn't slipping? Had your symtoms in a Datsun truck, no belt chirping to tip me off it was loose.
Tom Willmon near Mountainair, (mid) New Mexico, USA
Some days the only good thing on TV is the vase.
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ive replaced dozens of those 98-02 v6 accord alts. first they start making noise, then they stop charging. you'll know by the smell. they go out more often than ive ever seen on any other vehicle. if you do it yourself, there's 2 ways you can get it out of the engine bay. good luck.

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