Another bad alternator
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Cross-Country
Joined: Mar 2009
Posts: 61
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From: New Braunfels, Tx
Another bad alternator
Put a new alternator on back in December 2010. Started noticing the voltmeter on the dash going back and forth periodically between charging and showing a discharge....sometimes the battery light came on as well when showing a discharge. Checked all the wires on the alternator and they seem snug. Today while the truck was running, I pulled both negative cables and it died....so, it seems I have another bad alternator. This is a '95 w/ 185K miles and this is alternator number 6 (counting the orig.). Please provide some advice/troubleshooting as to why my truck seems to eat alternators. The original lasted about 6 years, so I've had 5 more on there since 2001. Would an additional ground off the alternator be helpful? Think I read on here once or was told by someone that might be an option.
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Cross-Country
Joined: Mar 2009
Posts: 61
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From: New Braunfels, Tx
Yes, I'm getting the lifetime warranty. But it seems there must be an underlying problem somewhere. I've gone away from the remans thinking they were the problem but this latest was a new Motorcraft.
Postmaster
Joined: Jan 2009
Posts: 2,667
Likes: 1
From: Glen Rose,Texas
IMHO you should have that alternator rebuilt by a local rebuilder.They will use the better parts and it will last longer than the crap made in Mexico.That is what I do.I have one on my truck and another waiting if this one goes down.It was rebuilt by a shop as well.
You can install a ground from one of the mounting bolts of the alt to the neg side of the closest battery,use heavy wire like 6 or 8.
You can install a ground from one of the mounting bolts of the alt to the neg side of the closest battery,use heavy wire like 6 or 8.
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Cross-Country
Joined: Mar 2009
Posts: 61
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From: New Braunfels, Tx
I may try that Barry. I still have the one I took off last in my tool box. I'll have the one on the truck load tested to see if it's bad. If so, I'll replace that one under warranty and have the older one rebuilt. How much does it cost to have one rebuilt? But, I'm still wondering why they keep going bad? What are the odds that one person could keep getting so many bad alternators? Like I said, this last one was a NEW Motorcraft.
Hotshot
Joined: Oct 2003
Posts: 17,799
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From: Ashland City, TN
if your swapping alternators and getting a new pully every time. Save me one!!!!!
I have the wrong pully on mine from the PO.
Its chewing up my serpentine belts.
I have the wrong pully on mine from the PO.
Its chewing up my serpentine belts.
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Senior User
Joined: Jul 2007
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From: Roseville MN
x2 on the connnectors at the alternator. I had a probelem with the coolant line rubbing down on one and it shorted it out.
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Thread Starter
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Cross-Country
Joined: Mar 2009
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From: New Braunfels, Tx
Alternator checked out good but they went ahead and replaced it to see if it would correct the problem. So, the problem has to be with my truck I'm assuming. Just not sure to go about how to determine what problem within my system would continue to blow alternators. Both batteries check out good.
Post Fiend
Joined: Oct 2003
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From: MICHIGAN
Alternator checked out good but they went ahead and replaced it to see if it would correct the problem. So, the problem has to be with my truck I'm assuming. Just not sure to go about how to determine what problem within my system would continue to blow alternators. Both batteries check out good.
Also check the fuseable links. They can be intermittent.
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Tuned
Joined: May 2010
Posts: 495
Likes: 130
From: Pleasanton, CA
You can't pull the neg batter cables off while it's running and expect it to keep running. Your truck runs off the batter the alternator is there to keep the battery or batteries charged. To test your alternator check voltage of barreled with engine off should read 12.5v or better then start your truck and measure again you should see 1.5 to 2.0 volts better somewhere around 14v. This means your alternator is working. If both or one battery reads 12v or upper 11v with motor off you may have bad battery or batteries?
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Cross-Country
Joined: Mar 2009
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From: New Braunfels, Tx
Jim, I've checked the wires on the alternator and they seem to be snug but I have not checked the fuseable links. What seems strange to me though is that I've replaced the alt. 5X since 2001....some have lasted a few months, some a year or two, and one lasted about 5 years. If I had a wiring issue all that time, why the inconsistency in how long it takes for it to affect the alternator? All of the previous ones failed load tests....this is the first on to pass.
Mike, thanks for the input. I'd always heard that if it stalls when the neg. cables are pulled, it's a sign the alt. is bad...think I even read that on this forum once. But, the guy at NAPA told me today to NEVER do that on a computer controlled vehicle.
Mike, thanks for the input. I'd always heard that if it stalls when the neg. cables are pulled, it's a sign the alt. is bad...think I even read that on this forum once. But, the guy at NAPA told me today to NEVER do that on a computer controlled vehicle.
Tuned
Joined: May 2010
Posts: 495
Likes: 130
From: Pleasanton, CA
dv,
You can definitely do some damage to your alternator by pulling the GND (negative) bettery cable while the motor is running. At the minimum you can damage the diode within the Alternator causing it to not work. I would also imagine further damage to other electronics.
I don't know how a motor can run without the battery connected even if the Alt is working. Everything runs off the batteries the Alt is just to keep the batteries charged. Years ago I had a flat bottom V-Drive boat that didn't even have an Alt I would just charge the battery each time I went on the water it would run 2-3 days just on the battery.
How long has it been since you replaced your batteries and did you replace them both at the same time? Also are they at least 850-900 CCA each? Maybe you have a battery issue and/or bad battery gounds?
Mike
You can definitely do some damage to your alternator by pulling the GND (negative) bettery cable while the motor is running. At the minimum you can damage the diode within the Alternator causing it to not work. I would also imagine further damage to other electronics.
I don't know how a motor can run without the battery connected even if the Alt is working. Everything runs off the batteries the Alt is just to keep the batteries charged. Years ago I had a flat bottom V-Drive boat that didn't even have an Alt I would just charge the battery each time I went on the water it would run 2-3 days just on the battery.
How long has it been since you replaced your batteries and did you replace them both at the same time? Also are they at least 850-900 CCA each? Maybe you have a battery issue and/or bad battery gounds?
Mike
Hotshot
Joined: Aug 2006
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We have used that test for years , if the alternator is working ,the motor will keep running ..
You can definitely do some damage to your alternator by pulling the GND (negative) bettery cable while the motor is running. At the minimum you can damage the diode within the Alternator causing it to not work. I would also imagine further damage to other electronics.
Laughing Gas
Joined: Sep 2007
Posts: 869
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From: Near Shenandoah Valley
I have heard the same thing about NOT unhooking Bats while running. I know several years ago we would start a vehicle and swap batteries with it running and charge up a dead one. Even the not quite local rebuild place says not to on new ones. A kid messed up the Alt. on my daughters '00 Honder with this. He said he wanted to see if it was charging. I told him the same thing Mike described as for checking output. Honder kept running. I have run into the same issue with starters if ya'll saw my thread. I ain't giving up my Alt. to these places and replacing with the junk they have. Keep everything clean and tite, after that it's the junk they sell IMO.