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Discussion Starter #1
I know there are a lot of sharp diagnosticians on this board so here is one for you:

I have a 2005 QP with 77,000 miles on it.

Today, for the first time, when the car gets warmed up the alternator light (red battery graphic) comes on and flashes. Doesn't happen when the car is cold.

It ONLY flashes when the car is at 3,000 RPM or above. Doesn't matter what gear or how much load. From what I can tell it is right at 3000 and this is consistent every time.

There is a whine that comes and goes. The whine is not RPM sensitive and is coming throught the sound system. Turn off the sound system and the noise goes away. The volume does not affect the volume of the sound. The whine does not correlate to the Alternator warning light coming on.

Can't hear in belt slipping noises or anything else unusual. Hasn't been happening long enough to tell if the alternator is charging the system or not.

Thoughts? Any help is appreciated.
Thanks,
Ken
 

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I bet on the belt...

It's slipping, but the serpentine belts don't squeel like the old ones... I have noticed mine slipping in the past, but just by the belt crumbs, no noise..
 

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Maybe, the voltage regulator gone bad. If you have volt meter, try to check voltage when revving more than 3000rpm.

pganmol
 

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If I were a betting man I would say your Alternator is on it last leg... might want to have it tested before your sitting on a roll back somewhere.
 

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Ohhh... Thats not too good...

The alternator sits in the middle of the engine, I think it is an engine out job... Cross your fingers that it is your battery or something...
 

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Discussion Starter #7
Thanks for the thoughts so far ..
If it is the Alternator gone bad; why doesn't the warning light come on until the car is pretty warmed up. And why only over 3K RPM?
 

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That is a shorted output diode in the alternator's diode pack, if the light gets brighter as you increase RPM.

Unless you are willing to get the alternator repaired somewhere, I would just replace it.

I haven't looked at the Maserati alternator but typically the field and output diode repairs are not so difficult although the more modern designs are "potted".
 

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Discussion Starter #9
That is a shorted output diode in the alternator's diode pack, if the light gets brighter as you increase RPM.

Unless you are willing to get the alternator repaired somewhere, I would just replace it.

I haven't looked at the Maserati alternator but typically the field and output diode repairs are not so difficult although the more modern designs are "potted".
Thank you Glenn
The light doesn't get brighter; It comes on a 3K RPM and flashes at a consistent rate and brightness.
 

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Thank you Glenn
The light doesn't get brighter; It comes on a 3K RPM and flashes at a consistent rate and brightness.
Probably the same issue, but the warning light is run via something else in the electronics to just flash when the alternator cannot provide insufficient current. The fact it comes on when the car is warm just means the diode is heat sensitive.

Most alternator pulleys are geared to provide max rated output at 2,400-3,000 RPM.

I would however expect the whine to change in frequency with the engine. Could be something to do with how the regulator is designed. The alternators typically have 3 phases so there are usually 9 diodes, 3 negative output rectifiers, 3 positive output rectifiers and 3 field diodes (to energize the field). Some alternators have fewer. But I am still willing to bet you have a diode gone, it is pretty typical in the case of no light at idle but the light coming on at speed.
 
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