alternato
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Joined: Jul 2003
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alternato
Need help understanding why my alternator is not charging.
We tried changing the battery and the alternator, but both of them are still good and the charge is the same when the meter is attached and the car is either off or on. By the way, I have a 99 Ford Expedition with a 5.4L engine. We were told to check into something called the ECU. Anyone have any suggestions for someone who would like to fix it themselves?
Troubled and confused
We tried changing the battery and the alternator, but both of them are still good and the charge is the same when the meter is attached and the car is either off or on. By the way, I have a 99 Ford Expedition with a 5.4L engine. We were told to check into something called the ECU. Anyone have any suggestions for someone who would like to fix it themselves?
Troubled and confused
Postmaster
Joined: May 2002
Posts: 3,028
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From: Annapolis, Maryland
alternato
Hi and welcome to FTE 
AFAIK, the ECU is the "Electronic Control Unit". It's not serviceable and usually costs more than the truck to replace. There's probably a simple solution to your problem. Have you had the alternator checked yet? I know Pep Boys has a bench tester for alternators. That may be something you want to look into. Also, NTB (National Tire & Battery) and Sears Auto Centers have something called a SABRE machine - it tests the charging system and will tell you what's wrong. The test only takes 5 minutes and costs $12.99.
XXL
AFAIK, the ECU is the "Electronic Control Unit". It's not serviceable and usually costs more than the truck to replace. There's probably a simple solution to your problem. Have you had the alternator checked yet? I know Pep Boys has a bench tester for alternators. That may be something you want to look into. Also, NTB (National Tire & Battery) and Sears Auto Centers have something called a SABRE machine - it tests the charging system and will tell you what's wrong. The test only takes 5 minutes and costs $12.99.XXL
Senior User
Joined: Feb 2003
Posts: 369
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From: Bronx, New York
alternato
Sometimes a regular elec. multimeter does not accurately check your charging system. I installed a 200 amp alternator about 6 mo. ago, and I got the same readings you did. I found out the alternator will only show a higher voltage "charge" under load, and a multimeter cannot do this. When the elec. system demands more current, the alternator senses this and steps up the output accordingly. You may not even have a problem, but get it checked anyway.
