alternator will only charge to 12v?

[1meanGTA]

i have 2 alternators, one stock and one iraggi 240a alt in my 98 eddie bauer (5.0 v8)

i hadnt had any trouble with the stock one until recently. i took it off to swap my iraggi back on, and while tightening the nut on the terminal post on top of the iraggi, the post broke off, and a hot 12v lead touched the case of that alternator. gave a pretty good spark. yes, i know it should not have been hot while i was doing this.

so i take it back out to send in and have dom fix the post, and after i put my stock one back on, it will only charge to 11.6-12v max. i thought maybe i did something to my battery with that short, so i swapped the battery and same thing. i have the stock alt positive to battery positive wire intact, and a 1/0 gauge on top of it. it was the 1/0 gauge lead that touched the alt, i dont think the stock wire ever shorted.

what did i do to my charging system??

 

[Turdle]

You may have blown a fuse?

http://www.explorerforum.com/forums/showthread.php?t=180814&highlight=power+layout

 

[1meanGTA]

that was the first thing i checked, i couldnt find any that were blown under the hood. i didnt check the instrument panel ones inside. any idea which fuse in particular it would be, as i didnt pull them all out and closely scrutinize, but i imagine a nasty short like that (it actually burned away part of the alternator casing) would have absolutely destroyed a fuse making it easy to spot.

 

[1meanGTA]

just went through and checked all the underhood fuses, they're all good. any relays or fusible links i should check?

 

[1meanGTA]

wow... just checked the battery with a multimeter, now i'm only showing 10.83v while sitting at idle. turn the truck off and it jumps up to about 11.4. shouldnt i have a warning light or something being that it doesnt appear to be charging at all?

 

[1meanGTA]

took the wires from the battery back off the alt and tested them, they both show exactly the same voltage as i show right at the battery, same when i use the alternator case as a ground. all of the connections there look tight.

 

[410Fortune]

When you turn your key to on, does the battery light come on? (determine if the bulb is still ok)

I suspect you blew the power feed to your internal voltage regulator, it may be a simple fuse but I am not 100% sure. First lets test:

Your voltage regulator gets a 12V+ and a - when you turn your key to on or run...if the voltage regulator is not getting its power then your alternator will not charge. The wire that supplies the 12V+ to the alternator goes directly through your dash pot, it is the same wire that the battery light is on.... if no voltage is being supplied you get a light.
If th ebulb is bad now it may not send the 12V

Check the voltage regulator + wire to ensure you are getting power with the key in run...

 

[1meanGTA]

the battery light comes on fine with the key switched to on, engine off. i pulled the harness from the regulator and tested it, it shows 11.56v with the truck off, when i switch it to on, engine off, it drops to about .1v.

i was testing it with the harness unplugged btw, do i need to strip the wires back and test it with it plugged into the regulator?

 

[410Fortune]

The voltage regulator has 3 wires correct?
1 may be 12V+ all times (hot)
2nd may be 12V+ acc on (+ with key on)
3rd should be ground

I am doing this from memory as I am at work, but it sounds like there is an issue with the power supplies to your votlage regulator...I dont think it should drop when you turn the key on...

Did you check all your dash mounted fuses?
let me consult my Explorer CDrom

 

[1meanGTA]

haven't checked any of the dash fuses, didnt think they'd have anything to do with it. will go do that now. was only the 2 wires going into my regulator harness.

 

[1meanGTA]

all of the fuses in the box on the drivers side are good.

 

[1meanGTA]

the regulator harness does have a spot for a 3rd pin in the center, but theres no wire going to it, so there may be an accessory wire on different years or different alternators. i looked on the cd-rom i have, but it seems to be very vague on a lot of things, it told me if my charging system warning light was functional to check the alternator to battery wire, and then to check the output of the alternator. i put a clampmeter (not entirely sure i was using it right, and its a cheap craftsman job) onto the nut on the charging post of the alternator, and was showing a steady 40a while it was running at idle, didnt change when i revved it to 3k rpm.

i couldnt find anything on the cd rom telling me whether the regulator should be showing 12v while in accessory with engine off.

 

[1meanGTA]

looking in my hayne's manual however, it says that with the ignition on, engine off, on that regulator harness there should be 12v at the a terminal and one volt at the i terminal, says neither is ground. i tested both of these with the harness unplugged and shows 12v at both. i'm assuming it is referring to with the harness plugged in, as it also says what they should show with the engine running, which is 12v at both.

anybody have any idea what the hells going on?

 

[BrooklynBay]

The alternator might have a shorted diode trio or a defective regulator. Take the alternator out to have it bench tested.

 

[1meanGTA]

the alternator that is installed now that wont charge, isnt the alt that i shorted a wire on. it worked fine when i pulled it out, put the 240a one in, shorted the wire, pulled it back out, put the stock back in, now it wont work.

 

[BrooklynBay]

Check these threads:
http://www.explorerforum.com/forums/showthread.php?t=196906
http://www.explorerforum.com/forums/showthread.php?t=180814

 

[1meanGTA]

had already seen the one with the fusebox diagram. i noticed the 175a fuse while looking for fusible links earlier, and its not blown.

will fusible links only burn up by the fusebox or do i need to remove all of the alternator wiring and look it over? also, it wasnt the stock wire that shorted, i'm almost positive it never touched a ground. it was the unfused 1/0 wire straight from the battery positive terminal.

 

[BrooklynBay]

Check the wiring from one end to the other with a continuity tester, and the battery disconnected.

 

[1meanGTA]

not entirely sure how to check continuity using my cheap wal mart multimeter. however i'm showing .7 ohms of resistance between the top of the terminal post (didnt take the wire off to check it the wire resistance alone) and the battery where that wire connects to the battery terminal. this was with the 1/0 gauge lead and both battery terminals disconnected. i'd show infinite resistance if a fusible link had burned right?

what is it that controls the voltage that is sent to the regulator, the ecm?

 

[BrooklynBay]

Nothing controls the voltage being sent to the regulator. The regulator is controlling the charge time on the rotor. The rotor's output gets magnetically transferred to the stator like a transformer. 0.7 ohms would be considered a closed circuit, and in this case the wire has continuity.