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#3559385 - 02/28/17 08:45 PM How to test voltage regulator/slip rings
98BoatCaptain Offline
Climber

Registered: 02/02/16
Posts: 944
Loc: Albuquerque NM
I've had an intermittent Battery light (and occasionally the voltage needle will dip low for a bit) for a week or so.

Signs seem to point to a possibly bad voltage regulator.

One of the service manual tests is to measure resistance between both alternator slip rings (field and B+, I assume) to see whether the voltage regulator is bad.

It looks like I'll have to pull the alternator and take the back cover off to do this test.

Do I have that right?
_________________________
1998 Mercury Grand Marquis LS
196k miles, many bits & pieces replaced, Peelformance White frown
Relay headlight harness & turbo encabulator

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#3560601 - 03/02/17 04:22 AM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
PHoganDive Offline
Over the Hill

Registered: 06/11/11
Posts: 2972
Loc: Mass, USA
It may be the brushes are stuck/worn, and not making steady contact with the slip rings. If the slip rings are OK, you can just swap the regulator/brush assembly.
_________________________

2006 CVPI w/120K, J-Mod, MSD COPs, BOC Tune, American Muscle Wheels, Magnaflow Stainless Catback Duals, 35% tint, UltraGuage, headlight relay harness installed w/ 80/100 watt bulbs.

1996 GMQ 116K miles, Bilstein shocks, otherwise stock (Retired 7/2011)

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#3560977 - 03/02/17 03:52 PM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
98BoatCaptain Offline
Climber

Registered: 02/02/16
Posts: 944
Loc: Albuquerque NM
I'll find out soon, possibly tonight. If indeed the brushes are worn, fortunately I can swap those out separately.

Be nice if that's all it is - new brushes are only about $10 shipped, vs. ~$50 for a new VR.
_________________________
1998 Mercury Grand Marquis LS
196k miles, many bits & pieces replaced, Peelformance White frown
Relay headlight harness & turbo encabulator

Top
#3561225 - 03/02/17 11:08 PM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
98BoatCaptain Offline
Climber

Registered: 02/02/16
Posts: 944
Loc: Albuquerque NM
Brushes look fine.

I tried to test the slip rings, but the procedure in the service manual makes no sense. It says to check resistance between each slip ring and the alternator case.

I get an open circuit reading (no ohms) on both slip rings, at all settings of the multimeter. It's supposed to read at least 200 ohms, else you need a new alternator.

WTF? How is my alternator working at all? Which it does, because I can measure a good 14.something volts at the battery's positive terminal with the engine running.


Edited by 98BoatCaptain (03/02/17 11:14 PM)
_________________________
1998 Mercury Grand Marquis LS
196k miles, many bits & pieces replaced, Peelformance White frown
Relay headlight harness & turbo encabulator

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#3561329 - 03/03/17 02:23 AM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
fordoldfart Offline
Climber

Registered: 10/27/09
Posts: 634
Loc: kansas
You want an open between the slip rings and the case. Depending on the amperage rating of the alternator you want from 1 to 3 ohms resistance from slip ring to slip ring. This testing can be done with just the voltage regulator / brush block removed. If this unit has 150,000 miles or more usually you will see one slip ring with a pretty deep groove and short brushes. A bad diode can turn on the battery light on but it is usually on permanently.

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#3561537 - 03/03/17 09:20 AM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
EZlivin11 Offline
Climber

Registered: 03/18/16
Posts: 997
Loc: Central Coast Of CA USA
+1^^^ Wear on the slip rings being the #1 issue with 150k. A bad diode would cause a battery drain with KOEO also.
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#3561721 - 03/03/17 10:46 AM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
98BoatCaptain Offline
Climber

Registered: 02/02/16
Posts: 944
Loc: Albuquerque NM
OK. Then either the service manual is wrong, or I'm reading it wrong. So what is the book talking about with the "at least 200 ohms from slip ring to case" thing? I'm referring to Pinpoint Test F5 from the charging system section.

Either way, it sounds like my alternator is fine. Open circuit between each slip ring & case. Resistance between slip rings was, as you say, a few ohms. I'm sure I have the regular 130 A unit, given it's a standard '98 Grand Marquis.

I'm not 100% sure how many miles are on this particular alternator. It is a Motorcraft unit, but has a "Remanufactured" label. Must have been installed some time before I got the car, at 60000 miles.

The slip rings looked decent. No uneven wear. Brushes were the same length (judging by the holes in them) and had a healthy amount of springiness, so it seems likely they're making smooth even contact when in use.

So...still don't know what the actual problem is.

Thanks guys!
_________________________
1998 Mercury Grand Marquis LS
196k miles, many bits & pieces replaced, Peelformance White frown
Relay headlight harness & turbo encabulator

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#3581089 - 03/20/17 09:30 AM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
98BoatCaptain Offline
Climber

Registered: 02/02/16
Posts: 944
Loc: Albuquerque NM
Any further thoughts on this?

The red "charging problem" light keeps illuminating intermittently. It'll stay on for maybe a minute or so max, sometimes just 10 seconds or so (can't really time it, busy driving!).

Every time I've looked lately, the voltage needle stays planted solidly in the middle of the gauge's range, so I don't think there's an actual charging problem. Light does not react according to engine rpm - it'll stay on either at idle or WOT, when it comes on.

I think my battery is fine, based on measuring voltage when off, BUT planning to stop by a VatoZone soon to get a second opinion.

Scratching my head otherwise. I've basically done everything the shop manual recommends for an intermittent charging light, short of replacing parts. At ~$50 for a voltage regulator and north of $100 for a reman'd alternator, I don't really care to take the "reconnaissance by parts replacemnet" approach.
_________________________
1998 Mercury Grand Marquis LS
196k miles, many bits & pieces replaced, Peelformance White frown
Relay headlight harness & turbo encabulator

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#3581281 - 03/20/17 01:08 PM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
McVic Online   content
n00b

Registered: 01/18/17
Posts: 20
Loc: USA
Following. Welcome to the 1998 intermittent voltage regulator fails! Been going through this ever since my car hit around 150k and changed the regulator once. My problem isn't quite like yours though. Every once in a blue moon mine doesn't charge upon cranking and the battery light comes on. Nothing remedies this but shutting the engine back off and cranking it again, then it's fine. A couple of times voltage went way above what it should.

I just watch that gauge like a hawk now. It's all I know to do.
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#3581497 - 03/20/17 04:31 PM Re: How to test voltage regulator/slip rings [Re: McVic]
98BoatCaptain Offline
Climber

Registered: 02/02/16
Posts: 944
Loc: Albuquerque NM
Well, we'll see what Vatozone says about the battery.

If the battery is indeed in good health, I guess a VR swap would be the less expensive option.

Now that I've had Mr. Alternator out and apart once, it's not a huge deal to do it again.

I have to replace the tolerance ring anyway. Broke that sucker real good on the first try at getting to the slip rings & brushes.

I don't seem to have any actual charging problem, though. There have been one or two times the volt needle wandered low when the light was on. But as I said, it stays in the "normal" indication mostly. A multimeter confirms proper output at the alternator B+ terminal, so yeah, I'm not sure what to think.

eta:
guy at the bottom of this thread:
http://www.crownvic.net/ubbthreads/ubbthreads.php?ubb=showflat&Number=1076218
seems to have a similar issue.


Edited by 98BoatCaptain (03/20/17 04:37 PM)
_________________________
1998 Mercury Grand Marquis LS
196k miles, many bits & pieces replaced, Peelformance White frown
Relay headlight harness & turbo encabulator

Top
#3581625 - 03/20/17 07:26 PM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
BigMerc96 Offline

I know nothing
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Registered: 06/05/10
Posts: 16132
Loc: I can see Detroit from here!
It seems that this is common on these early 6G alternators. Wonder why? I've seen the battery light come on for a few seconds twice now in my '98. It comes on just long enough for me to notice it, then it goes out. Not sure what to make of it, car only has 90k miles, but after 19 years I'm sure the alternator could use some freshening. then again, I have a functional 3G on the shelf in my garage, I could just retrofit that, the 3G is a great alternator even if it is less efficient.
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1998 Mercury Grand Marquis LS HPP ~88k miles, stock for now.

1997 Town Car Cartier ~140k miles, 70mm TB, Ported Plenum, Gutted Airbox, Mechanical Fan Delete, Contour E-fan Retrofit, Dual exhaust with Magnaflows, rear cat delete, MSD Ignition, KYB Gas-A-Justs, Marauder/HPP rear sway bar, P71 front bar, air ride reinstated, Blinker Mod, Projector retrofit, Caddy 4-note horn retrofit, Wood rim steering wheel retrofit, natural weight reduction.. Smashed 1/13/13....I fixt it..
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#3582065 - 03/21/17 10:29 AM Re: How to test voltage regulator/slip rings [Re: 98BoatCaptain]
98BoatCaptain Offline
Climber

Registered: 02/02/16
Posts: 944
Loc: Albuquerque NM
My alternator is "remanufactured" according to a sticker on it.

I don't know exactly when it was replaced. Some time before 60k miles, because that's when it became my car.

Since I haven't had any actual charging problems yet, maybe this is just something I'll learn to live with. >$100 for a reman replacement alternator is a bit rich for fixing a seeming indicator-only problem.
_________________________
1998 Mercury Grand Marquis LS
196k miles, many bits & pieces replaced, Peelformance White frown
Relay headlight harness & turbo encabulator

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