Howdy all. New guy here. Not really a Ford enthusiast, more of an opportunists. Picked up a 2000 Explorer XLS for my 16 year old son to drive. It looks and runs great but it needed a new alternator. Long story short, 3 shiny new alternators from AutoZone later, it still acts like it needs a new one. If I check voltage at the alternator, while running, it's never over 12.5V. As I turn on accessories, the voltage drops down to 11.7 and doesn't come back up. When I turn it off, the battery slowly creeps back to 12.5V. The 30 amp fuse is good as is the 175amp fusible link. Shouldn't I have 14+ volts out of a brand alternator?

 

Welcome to the forum!

Yep, you should see anywhere from 13.8-14.4 Vdc out of an alternator that is working properly. Sounds like you're going to need the charging system wiring diagram and start to do some testing to figure this one out.

Do you have the diagram already? If not, I can provide you a PDF of the diagram(s) from the factory service manual if you send me a Private Message with the request and an e-mail address for you.

-Rod

 

I already have the charging system schematic for it, thanks for the offer. I will just need someone who knows how to read one better than I do. From my limited knowledge, it all checks out ok. I have read threads on here with similar problems and they always seem to end with the 30 amp fuse, the 175 amp link or a bad ground. Mine all check out.

 

Does the Battery indicator on the dash ever illuminate?

I'm not sure how easy it will be to check these voltages with the engine running, but do what you can to compare against the following table.

<table border="1" cellpadding="3" cellspacing="0"> <caption>Normal Charging System Voltages </caption> <tbody> <tr> <th valign="bottom" align="center">Terminal </th> <th valign="bottom" align="center">A </th> <th valign="bottom" align="center">S </th> <th valign="bottom" align="center">I </th> <th valign="bottom" align="center">Alt B+ </th> <th valign="bottom" align="center">Batt </th> <th valign="bottom" align="center">Eng to Bat Gnd </th></tr> <tr> <td valign="top" align="left">Key OFF </td> <td valign="top" align="center">12V </td> <td valign="top" align="center">0V </td> <td valign="top" align="center">0V </td> <td valign="top" align="center">12V </td> <td valign="top" align="center">12V </td> <td valign="top" align="center">0V </td></tr> <tr> <td valign="top" align="left">Key On - Engine Off </td> <td valign="top" align="center">12V </td> <td valign="top" align="center">0V </td> <td valign="top" align="center">1-3V </td> <td valign="top" align="center">12V </td> <td valign="top" align="center">12V </td> <td valign="top" align="center">0V </td></tr> <tr> <td valign="top" align="left">Engine Running </td> <td valign="top" align="center">12V-
15V </td> <td valign="top" align="center">6-8V </td> <td valign="top" align="center">12V-
15V </td> <td valign="top" align="center">12V-
15V </td> <td valign="top" align="center">12V-
15V </td> <td valign="top" align="center">0V </td></tr></tbody></table>

 

No it does not. The gauge does continue to drop, but no light comes on. I decided to let it run till it died with a volt meter on the battery. I had all accessories on. At 9.5 volts the ABS light came on. At 8, the wipers slowed way down and headlights dimmed, but it kept running. Didn't die till I pushed the brake pedal when the meter read 5.4 volts. I will check those voltages when I get home tonight, thanks.

 

Have you had the battery load tested? If not...I'd start there.

 

Yep. 2 different batteries, both A-OK.

I just noticed, there's 7.5 amp fuse on the indicator light circuit that I missed. Have to check that out. If it's blown, that would explain why the light never came on. Is it possible that, if blown, it would stop the system from charging?

 

Yes, if that fuse also powers the alternator trigger circuit...

You are still guessing, complete the tests per the scale/table supplied... Philip

 

Pulled 7.5 amp fuse from position 15 in the fuse block, tested good. Put it back in, started the truck and everything worked perfectly. All voltages checked within the specs on the table that shorod provided. So with my multi-meter in view, I wiggled that fuse a little and the voltage would drop to 12.5 and come back up to 14.4 depending on how I pushed and pulled on it. For now, I wedged a piece of business card in next to the fuse that keeps it pushed to side that makes it work. Who'd uh thunk?

 

That's an interesting data point. I saw that fuse in the wiring diagram but it appeared to only be for the dash light, I did not expect that it provided feedback to the alternator. Thanks for identifying that functionality of it! I'm glad to hear you apparently know where the issue now lies. Seems like it should be a pretty easy fix which means you got a good deal on a nice Explorer! You may be able to pinch the fuse terminals together a bit to allow it to grab on to the fuse better. It's probably best to do so when the battery is disconnected.

-Rod

 

I've been on this site for years, and it never ceases to amaze me the amount of "corporate knowledge" available. Good Job and great answer - I'm really impressed, and from an observation standpoint - Thank You for the input.