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Last week I replaced my alternator because it was not working. I had changed it out previously 2 years ago but more importantly on had 4k miles on the truck since I don't drive it much. One week into the new alternator and it stops charging. Should I be looking at something else?

BTW the alt was a high output 3g not that it should matter.
 

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1988 FSB, 351W, Towing Package
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115 Posts
Last week I replaced my alternator because it was not working. I had changed it out previously 2 years ago but more importantly on had 4k miles on the truck since I don't drive it much. One week into the new alternator and it stops charging. Should I be looking at something else?

BTW the alt was a high output 3g not that it should matter.
I haven’t dealt with my alternator at all because I haven’t had any trouble with it but it’s always a great idea to check your grounds, if you haven’t yet start there


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some of the best starters and alternators are ones rebuilt by a well known rebuild shop. I'd say an OEM unit would be the best base for a rebuild; so a junkyard OEM large case 3g for your year/engine.
 

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I had a remanufactured 130A 3G from a local part store that died on me after only 1 month of service. It was a Motorcraft unit that had been serviced by AC Delco. One day it suddenly started overcharging at 18V and boiled my battery. I went through a series of tests and determined that the rectifier circuit was toasted. So was my battery. Parts store gave me a fresh alternator under warranty. A year later now and no problems, knock on wood. In hindsight, they probably should have covered my battery cost too, as it had been healthy until then.

For the few extra bucks up front, a unit with a warranty provides good piece of mind
 

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Yo First,
Alternator Failure Symptoms are a burnt stator. In many newer vehicles, The area around the rectifier on the back of the alternator plugs up with dirt and fibers, causing the unit to overheat. Rear alternator bearing failure may be caused by over tightening the belt or a seized belt tensioner. The bearing is retained in the alternator by either an aluminum ring or a plastic retainer, which under pressure, will collapse. Drive belt slippage may cause overheating and bearing damage. Thread damage on the rotor of the alternator is caused by improper pulley installation methods. Cracked terminal insulators are cuased by over tightening the terminal nuts. Improper changing of the alternator clock postion may result in broken brushes and brush holders..."
Source: by thirskauto.net via web.archive.org

Diode Leakage Test; "...To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first..."
Source: by assets.fluke.com

Diode Pattern Waveforms, Bad; "...This waveform was captured using the diode pattern test located in the engine tests menu. This particular alternator has a bad rectifier, causing an AC voltage to ride on top of the DC voltage signal. This AC voltage affected the pip and spout signals (Ford primary ignition signals) causing a no code driveability problem. The fix was to replace the alternator. This waveform was captured using the diode pattern test located in the engine tests menu. This alternator, like the previous alternator, has a bad rectifier. This is another example of how a bad rectifier can affect the diode pattern. The fix was to replace the alternator. This waveform was captured using the lab scope. This is a good example of how an alternator with a bad diode can affect other signals that the ECM looks at. In this case it is an IAC motor. When viewing waveforms that have a lot of hash always look at the alternator diode pattern as a possible cause..."
163797

Source: by omitec.com
 

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95 Bronco, 351W, E4OD, 4.56 gears, 35x12.50x15 Patagonia MTs. 94 Bronco 5.0/E4OD/1356/3.50 gears.
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Sounds normal, my F350 had several new parts (alternator and starter) fail back to back, same with the egr sensor on the Bronco. Rebuild your oem parts when possible or buy motorcraft. I've had better luck with having a local shop rebuild electric components rather than buying them new.
 

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Sounds normal, my F350 had several new parts (alternator and starter) fail back to back, same with the egr sensor on the Bronco. Rebuild your oem parts when possible or buy motorcraft. I've had better luck with having a local shop rebuild electric components rather than buying them new.
Normal is having new parts fail constantly? Concerning state of affairs.
 

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95 Bronco, 351W, E4OD, 4.56 gears, 35x12.50x15 Patagonia MTs. 94 Bronco 5.0/E4OD/1356/3.50 gears.
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439 Posts
Normal is having new parts fail constantly? Concerning state of affairs.
Yes and yes. My new motorcraft rear brake spring kit didn't even work this morning. The upper springs were tempered wrong or made of the wrong material, they refused to stretch the 1/2" to install and bent instead. Had to put vice grips on them to do that. The old spring went on first try with 1/4 the effort. I worked as a mechanic for years, it's definately a case of chinese random quality parts.
 
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