2002 Ford Explorer alternator

Tiny
PENABOY
  • MEMBER
  • 2002 FORD EXPLORER
How long does a refurbished alternator last? We barely bought it two to three weeks ago and it already went out or could there be something wrong with the engine or could there be something wrong with the wiring.
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Tuesday, May 12th, 2015 AT 8:05 PM

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Tiny
CARADIODOC
  • EXPERT
Depends on what happened to the original generator and the new one. Bearing failure is due to mileage and is not likely to happen so soon on the new one as long as they were replaced when the unit was rebuilt. Brush failure is also related to mileage. Throughout the '90s Ford had a pretty nice design where the voltage regulator was bolted to the back of the generator, and when you removed it, the brushes were right there too and easy to replace. I guess the engineers didn't like that ease of diagnosis and service because by 2000 they put another cover over the regulator and test points to increase the difficulty.

If you're getting a maximum of exactly one third of the generator's rated current, one of the six diodes has failed. If the same thing happened to both of them, replace the battery. Due to how these voltage regulators work, the generator's output "stator" winding develops a lot of voltage spikes that can damage the diodes, voltage regulator, and interfere with computer sensor signals. The battery is responsible for damping and absorbing those voltage spikes but as they age and the lead flakes off the plates, they lose their ability to do that. GM owners are very familiar with this problem. It is responsible for going through four to six replacement generators in the life of the vehicle. The battery should be okay if it is less than about two years old.

You also have a 15 amp fuse inline with one of the three wires in the smaller plug on the generator. That wire used to be the yellow one. It should have 12 volts on it all the time. If that fuse has corroded terminals it could cause intermittent operation.
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Tuesday, May 12th, 2015 AT 10:08 PM
Tiny
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We had a mechanic come and he doubts it could be the wiring because the check engine light doesn't go on. He checked the fuse box and everything.
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Tuesday, May 12th, 2015 AT 10:28 PM
Tiny
CARADIODOC
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?

The Check Engine light doesn't have anything to do with the generator. There are over 2,000 things the Engine Computer checks and can set diagnostic fault codes for. Only about half of those relate to something that could adversely affect emissions. Those are the codes that turn on the Check Engine light. There can be codes stored in the computer even though the Check Engine light isn't on.

You still haven't told me what the symptoms are or why you think the new generator has failed. What kind of problems are you having? How was the charging system tested?
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Tuesday, May 12th, 2015 AT 10:50 PM

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