98 Grand Marquis Alternator light

My alternator light comes on occassionally. I replaced the battery because it was the original. Not bad for a 9 year old battery. The light still comes on intermittently. Anyone know what it could be? Is
it the obvious bad alternator or could it be someting else less expensive (wishfull thinking)
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mstrspy wrote:

If the alternator is also that old, it's probably on the way out, although it could be corroded/loose connections or worn/loose belt (tensioner). Don't trust the idiot light; get a cigar lighter plug-in voltmeter for $15 or so, and go by that.
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Better idea... take the 15 bucks and put it towards a decent DMM. Once you have it in hand, use the instruction book to learn how to perform voltage drop testing.... Having a DMM and KNOWING HOW TO USE IT TO ITS ABILITIES will (and I kid you not) turn you into a repair wizard....
The DMM is the most underused, misunderstood tools that anyone can possess....

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Sharon Cooke wrote:

The alternator on your GM is pretty durable, and very repairable. The occasional battery light is because the brushes are likely near the end of their life though. Get a brush holder and brush kit along with a regulator from a "real" parts store like NAPA. ~$30, maybe. Pull the alternator, replace the entire "square" looking assembly on the back of the alternator (4 torx screws). It should then outlast the car. If the belt is OEM, replace it along with the tensioner. This ~$100 system tune up should keep your GM reliable for quite some time.
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Do I have to remove the alternator to do this? Admittedly I haven't looked at it very closely yet. M
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Thear does have a volt meter. The volts read okay. An ammeter woud have been better .
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mstrspy wrote:

A voltmeter is way more reliable & informative than an ammeter. See: http://www.egauges.com/ATM_Tips.asp?TipPage=voltmeterammeter.htm
When you say, "volts read okay", that means what to you? Are you getting around 14.5 volts just after startup, and 13.4~14.0 volts after warmup?

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From: snipped-for-privacy@verizon.net (mstrspy)
My alternator light comes on occassionally. I replaced the battery because it was the original. Not bad for a 9 year old battery. The light still comes on intermittently. Anyone know what it could be? Is it the obvious bad alternator or could it be someting else less expensive (wishful thinking)
=====> don't feel like the lone ranger on this one. i've got a 99 crownvic P-71 that has done this since the day i picked it up. the light will come on for no reason and may stay on for a short period of time. (minute to 5 minutes or more) then go out. usually, this happens when i'm cruising at highway speeds.
at first, it bothered me. i checked the voltage out as well as the volt meter on the dash.
i've never had any electrical problems or a discharged battery with this car. i figure that sooner or later, the cause would show up, but it hasn't yet.
being a P-71 series, i figured that maybe someone screwed up the wiring taking out the special equipment or something.
~ curtis
knowledge is power - growing old is mandatory - growing wise is optional "Many more men die with prostate cancer than of it. Growing old is invariably fatal. Prostate cancer is only sometimes so." http://community.webtv.net/PALMER_ENT/doc
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Thanks for your experience on this. I will probably ignore the problem. I also have a chek engine light due to insufficient catalyst. I will probably need to fix that soon to pass inspection.
On Fri, 19 Jan 2007 19:57:18 -0600, PALMER snipped-for-privacy@webtv.net (c palmer) wrote:

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Thanks for your experience on this. I will probably ignore the problem. I also have a check engine light due to insufficient catalyst. I will probably need to fix that soon to pass inspection.
=====> my theory on the Alternator light is that there is a back feedsomewhere that is causing the light to shine. for some unknown reason, the back feed stops and turns the light out. but what is causing it???
i can only speak from my case. i've had this particular car for about 2 years and it's done it since the day i've gotten it. i have multiple cars to drive and this car may stay parked for several months and not started. but each time i go out and start it, it fires right up, which means that the battery was getting the charge it needs. so.......... there are mixed signals somewhere. the light comes and goes, but yet, the end result is that it hasn't affected the vehicle from starting. i wonder if anyone else has had a similar experience?
~ curtis
as a post note here. i have two P-71's and the other vehicle doesn't do this and they are the same year. the electrical checks that i've performed between the two cars have checked out so far and there is no hard or soft codes reflecting what this problem is.
knowledge is power - growing old is mandatory - growing wise is optional "Many more men die with prostate cancer than of it. Growing old is invariably fatal. Prostate cancer is only sometimes so." http://community.webtv.net/PALMER_ENT/doc
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