Alternator Trouble Again
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Fleet Mechanic
Joined: Jul 2003
Posts: 1,570
Likes: 20
Alternator Trouble Again
I replaced the brushes on my alternator and everything checked out okay. Now the Amp light is back on, gauge is on the "O" in NORMAL have 12.83 volts at the battery engine running at idle , 12.56 engine off. Checked my battery cells with a Refractometer, all okay. The marine battery charger/maintainer says everythings okay. On the back of the alternator one of the voltage regulator screws says, "Short to Test" what does this mean?
Also I'm using this check list. It's a 4.0L 94 with 95 amp alternator. When the Alternator is running it sounds like a sewing machine, its always been that way, but maybe noisier than when new. http://www.starteralternator.com/alt...ting_check.htm
Also I'm using this check list. It's a 4.0L 94 with 95 amp alternator. When the Alternator is running it sounds like a sewing machine, its always been that way, but maybe noisier than when new. http://www.starteralternator.com/alt...ting_check.htm
Last edited by Aftrmidnite; Jul 13, 2005 at 08:54 AM.
Elder User
Joined: Dec 2004
Posts: 718
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From: North Jersey, New Jersey
My alternators bearings went last year and the charge gauge was on the O in Normal as well. Only at idle did the AMP light come on though but at idle I heard a rythmic squeaking and thats when charge was insufficent and the light came on. For the last 2 years there was a squeaking but I thought it was just a dry belt it turned out the alt bearings wore until the alt couldn't charge the battery.
I would also compare the prices on a new alternator if replacing the defective part costs more then half the value of the alt your probably better off getting a new one or to save even more money like I did an aftermarket rebuilt one.
I picked up a Duralast at Autozone and have had no problems they also refund a core charge of $20.00 to - $40.00 when you give them your old alt depending on the model.
I would also compare the prices on a new alternator if replacing the defective part costs more then half the value of the alt your probably better off getting a new one or to save even more money like I did an aftermarket rebuilt one.
I picked up a Duralast at Autozone and have had no problems they also refund a core charge of $20.00 to - $40.00 when you give them your old alt depending on the model.
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Fleet Mechanic
Joined: Jul 2003
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I have an Napa near me, has anyone gotten an alternator there? Can't understand how the battery could be bad, as I checked the Specific Gravity of each cell with a refractometer and it takes a charge fine. I've worked with wet cells for years on UPS for computers. Bearings on the Alt. are smooth and quiet, but it's not worth putting a voltage regulator in it.
Posting Guru
Joined: Jul 2004
Posts: 2,416
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From: Mitchell, SD
Here is what is happening, (and what will happen if you don't replace the battery with the alternator
1. Voltage regulator goes out on alternator.
2. Battery is overcharged numerous times
3. Finnally the dummy light comes on and you find out the regulator is toast.
4. You replace the alternator.
5. A couple months later your battery finnaly gives up the ghost.
6. You replace the battery, but the damage to the new alternator's regulator has been done.
7. A couple months go by and that dang alt light is on again because the reg is toast again.
Been there, done that, don't want to do it again.
1. Voltage regulator goes out on alternator.
2. Battery is overcharged numerous times
3. Finnally the dummy light comes on and you find out the regulator is toast.
4. You replace the alternator.
5. A couple months later your battery finnaly gives up the ghost.
6. You replace the battery, but the damage to the new alternator's regulator has been done.
7. A couple months go by and that dang alt light is on again because the reg is toast again.
Been there, done that, don't want to do it again.
Senior User
Joined: Apr 2004
Posts: 312
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From: Lanham,MD
I changed mine to a Explorer 130 amp alt and its charging about the same as the 95 Aerostar at slightly over 14 volt
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Senior User
Joined: Jul 2004
Posts: 425
Likes: 8
From: Park Ridge, Illinois
Just swap out the alternator and you should be good to go (assuming that you don't get a bad rebuilt alternator like I did!! Everything is cool now.). Good luck. i know how frustrating this can be!
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Thread Starter
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Fleet Mechanic
Joined: Jul 2003
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It could be the bearinging are bad when you put a load on them, seen plenty of motors like that, even in brand new equipment. or the armature could be separating. Wouldn't show up in hi-pot or meg test. The battery will get checked again tomorrow, it is taking a charge tonight with the tender, and I've never had it misdiagnos a battery. Wish I had the battery load test device, we had at work.
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