Bad Alternator??
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Joined: Mar 2008
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Bad Alternator??
Hey guys, I have a 2003 Expedition with the 4.6 Motor. Earlier today I started the truck and noticed that it had a battery light on, and says check charging system, the light is solid and not blinking. After looking more into it I noticed a whine coming from the engine. There are no OBDII codes, but I am leaning towards the alternator. Any ideas from the experts?
Also, if it is the alternator, how hard of a replacement job is that for a rookie wannabe mechanic?
Also, if it is the alternator, how hard of a replacement job is that for a rookie wannabe mechanic?
Hotshot
Joined: Jan 2008
Posts: 13,144
Likes: 11
From: Rochdale MA
If you have a meter you can measure the voltage while the truck is running, You should have 13.5-14V, Put your headlights on and test the voltage should be the same. I have a 97 and changing the alt is not to bad of a job, not as easy as my 01 Super Duty but not to bad non the less.
You can also have the alt tested at Auto Zone or one of those type stores too.
You can also have the alt tested at Auto Zone or one of those type stores too.
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Freshman User
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update: just got back from Oreilly, they said the alternator was bad, it's putting 12.45 to the battery, and their reader says it has a bad diode. He said basically with a bad diode that it would be like leaving the lights on constantly, and overnight it would kill the battery. Does that sound correct?
Laughing Gas
Joined: Jan 2003
Posts: 1,082
Likes: 40
From: Melbourne, FL
You should replace based on the voltage output. Really easy to do, finally a manufacturer made something easy to replace. As for the diode, I know the alternator has a diode that turns on the battery light. A replacement I installed last year would charge perfectly, but had a bad diode and the light would stay on.
Mountain Pass
Joined: Sep 2005
Posts: 164
Likes: 1
From: Ponte Vedra Beach, FL
Not sure, but depending on the miles on your expy, I would say you need to replace the alt. I'm not sure you can even replace any of the internal parts anymore like the old days when you could separately replace the diode set, brushes, even bearings, for $10-15 instead of dropping $150 for a rebuilt (in Mexico) unit.
Hotshot
Joined: Feb 2003
Posts: 11,537
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From: Long Beach, Ms.
It is 9 years old so I would go ahead and replace not fix.
2003 Ford 4.6 alternator - Google Search
2003 Ford 4.6 alternator - Google Search
Senior User
Joined: Feb 2004
Posts: 317
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From: Omaha, Nebraska USA
The diodes turn the Alternators alternating current in to DC current. The burned out diode is like a lite short draining the battery.
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Hotshot
Joined: Jan 2008
Posts: 13,144
Likes: 11
From: Rochdale MA
update: just got back from Oreilly, they said the alternator was bad, it's putting 12.45 to the battery, and their reader says it has a bad diode. He said basically with a bad diode that it would be like leaving the lights on constantly, and overnight it would kill the battery. Does that sound correct?
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