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

Aug 30, 2007 2 Replies
A

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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J

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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S

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

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