Alternator ripple from bad diode?? Faulty dash light?? Belt issues?? 1991 240sx batt light on dash

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AWN - 30 Aug 2007 05:01 GMT

Hi there,

I have a 91 240sx with a BATT light on the dash and I have some questions:

1) Will alternator ripple (say over .5A AC) cause the light to go on?
2) Would a slipping belt cause this?

The battery was just replaced under warranty as a new one failed after 6mo
The alternator tests ok at 14.6VDC
There are no problems at idle or starting the vehicle
The BATT light is on in both neutral and drive but tends to dim a little
when going easy on the throttle (leads me to believe maybe ripple due to a
bad diode)

Thoughts?? I have yet to test for ripple or to test the amperage of the alt
(I wanted to ask first what your thoughts were.

Thanks,
Andrew.

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jjsant@yahoo.com - 30 Aug 2007 21:19 GMT

> Hi there,
>
[quoted text clipped - 15 lines]
> Thanks,
> Andrew.

If your voltmeter is good, you can set it for AC and check the AC
voltage on the battery (i.e. ripple.) I have seen alternators put out
adequate current (maintain adequate voltage) yet have one bad diode
section and the light on. This was on the old 60amp GM units.

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Steve Austin - 31 Aug 2007 11:35 GMT

> Hi there,
>
[quoted text clipped - 16 lines]
> Andrew.
>

I'd put a scope on it. I had exactly that problem on my 92 240sx.

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