Alternator problem?

[ajc2103]

i have a '99 explorer xlt that has been sitting for a good 6 months now. Battery was dead so I replaced it but found that when I start the car that the battery wasnt charging. I replaced the altenator as the old one was bad but now that the new altenator is installed the battery still isnt charging. I took a voltage reading off the altenator and it is only kicking out .6 volts, i then removed the altenator and took it back to the auto patrs store as I thought it was bad but when they tested it on the machine it was kicking out 14.5 volts. checked all the fuses and they seem fine. Battery light indicator on the dash is lit and im at a loss for what the problem can be. any thoughts would be greatly appreciated.

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the stock 95-01 section. Check the wiring on the charging system.

 

[98 5oh XLT]

Check your plug on the voltage regulator. I had an issue about 4 months ago that ended up taking my truck down for almost 2 months, it also fried my alternator. Well i got it back up on the road, it appeared to be showing charge then all of a sudden my volt gauge went about halfway down. turned out the plug on my regulator was not as snug as i prior thought. Also another thought, is there corrosion on the alternator to batt line? Id pull that off, clean it up, and make sure its snug down. Only other thought i might have is that your belt is slipping on the pulley of the alternator but i think that would be noticable. In my opnion the guys @ autozone and such dont typically test alternators properly because @ an idle an alternator is not working at its full potential. best way i have known how to test them with a volt ohm meter is to have a friend rev it to 1500-2000 RPM then check, since when your driving thats where your most common engine speed is.


/hopethishelps

Oh one more thing, check your terminals. It should be a fairly simple system, then again i didnt have anything go majorly wrong with mine so someone more educated might have something more to say.

 

[jremington59]

There's also a fuse in your fusebox and another in the one under the hood. Check your manual for fuse numbers.

 

[ranger7ltr]

Did you check the megafuse under the hood?

It is on the engine side of the under hood fuse/relay panel on the drivers side of the engine bay...It has its own little flip up cover and if it is blown you get no battery voltage to the alternator to make the unit start charging...

Since you checked the alternator on the truck did you check the positive terminal stud on the back of the unit where the battery voltage line is attached? If you do not have battery voltage there you either have a dead megafuse or a broken voltage line from the battery...

 

[lizardflats]

Did you check the megafuse under the hood?

It is on the engine side of the under hood fuse/relay panel on the drivers side of the engine bay...It has its own little flip up cover and if it is blown you get no battery voltage to the alternator to make the unit start charging...

Since you checked the alternator on the truck did you check the positive terminal stud on the back of the unit where the battery voltage line is attached? If you do not have battery voltage there you either have a dead megafuse or a broken voltage line from the battery...

I have no charging from the alternator and there is no battery voltage on the alternator stud. My battery light on the dash goes out when I start the engine, but the battery voltage starts dropping from a fully charged ~13.6V down to 12.8 or lower and keeps going down.

Where do I find the "megafuse"?

I'm also going to try and trace the alternator stud wire to see where it might be broken or if it's a corroded connection at the positive battery terminal.

 

[donalds]

I have no charging from the alternator and there is no battery voltage on the alternator stud. My battery light on the dash goes out when I start the engine, but the battery voltage starts dropping from a fully charged ~13.6V down to 12.8 or lower and keeps going down.

Where do I find the "megafuse"?

I'm also going to try and trace the alternator stud wire to see where it might be broken or if it's a corroded connection at the positive battery terminal.

Sounds like it maybe time for a new alternator

 

[lizardflats]

I have no charging from the alternator and there is no battery voltage on the alternator stud. My battery light on the dash goes out when I start the engine, but the battery voltage starts dropping from a fully charged ~13.6V down to 12.8 or lower and keeps going down.

Where do I find the "megafuse"?

I'm also going to try and trace the alternator stud wire to see where it might be broken or if it's a corroded connection at the positive battery terminal.

Update: It turns out I DID have battery voltage on the alternator stud, but it never changed when the engine was started.
I got a new 130 amp alternator today and it's fine now. Runs ~14.5V or so when the engine is running.