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Car Forum / Ford / Ford Cars / January 2007

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98 Grand Marquis Alternator light

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mstrspy - 17 Jan 2007 03:03 GMT
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)
Sharon Cooke - 17 Jan 2007 03:54 GMT
> 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)

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.
Jim Warman - 17 Jan 2007 05:12 GMT
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....

>> My alternator light comes on  occassionally. I replaced the battery
>> because it was the original.  Not bad for a 9 year old battery. The
[quoted text clipped - 6 lines]
> Don't trust the idiot light; get a cigar lighter plug-in voltmeter for $15
> or so, and go by that.
Tom Adkins - 17 Jan 2007 05:47 GMT
>> My alternator light comes on  occassionally. I replaced the battery
>> because it was the original.  Not bad for a 9 year old battery. The
[quoted text clipped - 6 lines]
> (tensioner). Don't trust the idiot light; get a cigar lighter plug-in
> voltmeter for $15 or so, and go by that.

 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.
mstrspy - 18 Jan 2007 00:04 GMT
Do  I have to remove the alternator to do this? Admittedly I haven't
looked at it very closely yet.
M

>>> My alternator light comes on  occassionally. I replaced the battery
>>> because it was the original.  Not bad for a 9 year old battery. The
[quoted text clipped - 14 lines]
>belt is OEM, replace it along with the tensioner. This ~$100 system tune up should
>keep your GM reliable for quite some time.
mstrspy - 18 Jan 2007 00:01 GMT
Thear does have a volt meter. The volts read okay. An ammeter woud
have been better .

>> My alternator light comes on  occassionally. I replaced the battery
>> because it was the original.  Not bad for a 9 year old battery. The
[quoted text clipped - 6 lines]
>(tensioner). Don't trust the idiot light; get a cigar lighter plug-in
>voltmeter for $15 or so, and go by that.
Sharon Cooke - 18 Jan 2007 03:57 GMT
> Thear does have a volt meter. The volts read okay. An ammeter woud
> have been better .

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?

>>>My alternator light comes on  occassionally. I replaced the battery
>>>because it was the original.  Not bad for a 9 year old battery. The
[quoted text clipped - 6 lines]
>>(tensioner). Don't trust the idiot light; get a cigar lighter plug-in
>>voltmeter for $15 or so, and go by that.
c palmer - 20 Jan 2007 01:57 GMT
From: blank@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 crown
vic 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
mstrspy - 20 Jan 2007 02:53 GMT
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.

>From: blank@verizon.net (mstrspy)
>
[quoted text clipped - 26 lines]
>invariably fatal. Prostate cancer is only sometimes so."
>http://community.webtv.net/PALMER_ENT/doc
c palmer - 20 Jan 2007 23:13 GMT
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 feed
somewhere 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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