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Zero volts from the alternator

donstevens

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City, State
Clearwater, FL
Year, Model & Trim Level
2006 XLT V8
Another weird electrical issue thread

My daughter's Explorer had been giving random dash warnings (low tire pressure, check charging system) for weeks. Then the other night the dash flicked, the lights went out, the trans went to limp mode all within a block of the house. She limped it home and while still running off the battery, all lights and dash were dark. Looked like a classic alternator failure to me.

I bought a replacement alternator from Adavance at 5pm on Christmas eve and planned to replace it the day after Chrismas.

I get the old alternator out, take it to Advance to verify that it had failed. They put it on the test rig and it tests OK. Because the issues had been intermittent I decided to install the new alternator anyway figuring it was the classic "the car is never sick when the mechanic is around." Meanwhile, I also charged the dead battery.

After wrestling with the belt tensioner I get it all back together, it starts fine, no dash lights, and then about 30 seconds later the "check charging system"
light comes back on. I recheck all of the connections and it all looks good. I drive the car to Advance on the battery and they put their gizmo on it. Zero volts form the alternator.

They are willing to let me try another alternator but that was a lot of work. Plus, since the old one checked out OK, something else is wrong. The Advance clerk suggested a fusable link between the fuse box and the alternator is bad.

Does anyone have any idea where that fuseable link is?

Is there a specific fuse or relay in the fuse box that relates to the alternator?

Anyone have a diagram of the fuse box? I have no owners manual. I bought the car used from a dealer (why do they often steal the owners manual anyway?)

Any ideas are welcome as this fricken car is driving me crazy. It is a shame. the engine runs great but the trans is goofy and the electrical system is goofy.

Don
 
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EXPLORER04

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04 XLT
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fordbluefamily

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2010 Mounty, 04 Mounty
How old is this battery? on our 2010, when the battery gets about 3 years old, it will crank the vehicle fine albeit a little slower, but will cause all of the systems to start up goofy, if at all. Have your battery checked for its cranking amps. Even the expensive Interstate Megatron+ we bought for it 3 years ago needed replaced this summer due to this. These things are hard on batteries.
 
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MotorCityFats13

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Flatrock MI
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2007 Explorer XLT 4.0L
even with a dead battery the alt will still try to charge it... if the alt is showing 0vdc then either it is dead or there is a break in a wire or the PCM which controls when the field is activated is faulty... step 1 is to take the alt to the auto parts store and have it tested... no reason to jump off the steps list and go out of order this will make you pull out all your hair.... if you had a 4.0 removing the alt is like a 10 minutes job... I dont know the layout of the 4.6 but it looks about the same.... if the alt was working you will get a 14vdc reading with a multimeter placed on the alt case and charging stud... if this does not match at the battery then the main charging lead is faulty... if the alt tests fine at the parts store then either the pcm or charging lead is bad... but from the pics it looks to only have 1 3 wire plug and no dedicated single wire for the field activation
 
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wsar10

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several JEEPS
If the battery is bad you can very well see nothing from the Alt. Your batt could now be in a failure mode that has a result of reversed polarity, this would present itself as "0 volts" due to voltage sag.
 
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