Voltage Issue's! any idea's?

[XxxMonoxideChild]

the entire time ive owned the explorer, the voltage gance liked to dance around. not fast or anything, or jumpy, but i wouldnt be surprised to watch the voltage gauge drop from 14.5 down to 8-9 volts just sitting at a stop sign.

well since its allways done it, but never actually done anything to make me think it ACTUALLY was running on 8 volt's, i assumed faulty sending unit and kinda blew it off.

that changed.. lol. about a week ago, i was waiting outside while my g/f ran into a store for something. noticed the low voltage, then suddenly the radio turned off! that got me worried, cause right away i knew the truck might die, and it WASNT just a bad sending unit.

i ordered the alt, picked it up, but hadnt had time to install it. well, my g/f took the truck out into chicago yesterday for work, she called me saying the radio shut off, and the truck is acting wierd. i told her to leave the radio off, turn the lights, and a/c off, and pray she makes it back... she called back 5 min later, she didnt make it back... it died coming to a stop i guess.

it took her over an hour to find someone to assist with a jump start. (i at least tossed a set of jumpers in it just in case) and she was able to get it home thankfully.

well i swapped out the alt last night, but the voltage is still going as low as 7 volts at times! (i allways thought a car couldnt even run on anything less then 8 volts?) ive also very recently replaced the battery, and battery cables, and all connections are tight. wiring itself isnt damaged or gunked up.

 

[MrWizard]

My first effort would be to check the voltage with a handheld voltmeter.
At the battery, with the engine running. Just to be sure the actual
voltage is dropping.

And check the serpentine belt tension ( although I'm assuming you would
have noticed if the idler tension was weak when you replaced the
alternator) .

 

[yellowcat]

who tested your old alternator. Did you buy an autozone alternator?

 

[XxxMonoxideChild]

i checked the amperage at the alt on my 1st alt, along with the current replacement. factory gauge was coorect on the low voltage. even today, it dropped so low, my blinkers wouldnt even work.. till i beat the hell out of it, then the voltage came back up.

serpentine is tight for sure, not loose at all. the new alt was purchased from auto zone. and i charged the battery before hand so it had a full charge before starting it like the alt directions called for. (which ive never had to do on any other alt swap, but figured it wouldnt hurt)

any other idea's? this thing is driven 200+ miles every monday, and thursday by my g/f, and i dont want her to get stranded out in chicago for a 3rd time in this truck. i dont even know what else i could replace? replaced everything that i would think could cause this, hence why im looking to the forum for help.

 

[Tbars4]

...I would first pull the alt. and battery , then have them bench tested..

...If it is good, either your alt. wiring harness has an issue or your neg./pos. cables are bad...

 

[XxxMonoxideChild]

i actually had the factory alt tested when i dropped it off for a core, and they said it was it working order, but since i allready installed the new one, i decided screw it. the old battery is currently in my beater probe working great, so thats kinda confusing, but i figured it would work to test it. cables are all new, as are the battery and alt. hence why im so confused over this..

 

[Tbars4]

...The battery cables were both replaced with new cables???...that only leaves your alternator wiring harness...

 

[XxxMonoxideChild]

well it was doing ok for a week, then of course, while my g/f was in chicago again, it died. i left work, jumped it, made it about 30 miles, and stalled out AGAIN... had to have it towed back again... thats over $700 in tows for this pile this month!

i cant believe the amount of problems we have had with this truck since getting it. the previous owner mentioned he had replaced the battery twice int he past year also, but said he drove it maybe once a month at most (very old, lived in a retirement home) so im thinking this was a ongoing issue before we got it. it seems to do fine if your just doing basic local driving, but the long, hour + non stop drive's is when it has its issues.

 

[beauboy]

Has a tech at Autozone tested your elec system with their cart? If so, surely they can't tell you that everything is fine.

Other than that, take it to Ford for a diagnostic readout. It might cost a few $ but it'll be much cheaper than $700 in tows.

 

[Tbars4]

...The crash carts they hook up to your charging system are usually wrong...Several times I have seen them show the system as good, and a bench test of the individual parts show that indeed a part was failing...

 

[Turdle]

Is there an alternator , or, charging system fuse?

 

[wyochimneysweep]

you probably got a bad ground from frame to engine block or frame to chassis. or even a bad ignition relay or the ignition switch itself

 

[XxxMonoxideChild]

ive had everything tested so far off the car, as in bench tested. i havent had them do the test while everything was installed actually on the car. but since you mentioned it. ill charge up the battery, and bring it there, and see what they can tell me.

ive thought about adding a ground straight from a mounting bolt on the alt, and have it going to the frame. that was my next thing i was gonna try actually, before i started tearing apart all the rest of the wiring.

i hadnt checked or even thought of the ignition relay or ignition switch. any way to test these? and how would that effect it not charging or holding a charge? im not saying your wrong. just never knew they would have anything to do with the charge system.

:edit:
tried adding a 4 gauge cable from one of the alt mounting bolts, directly to the battery neg. no change.

 

[Tbars4]

...Your negative cable from your battery, to your frame rail, then to your motor, makes this ground for you..As you had mentioned before, this is a brand new cable...:scratch:

 

[XxxMonoxideChild]

well i ripped out the alt, and battery, and had them both bench tested again, at a different autoparts store. the alt had a bad diode. so i got another new one. battery still read good.

ripped out all the positive wire going from the alt, to the starter relay, replaced the entire length with new 4 gauge wire. left the original wire from the starter relay, to the battery, and added another new 4 gauge also. i also replaced the starter relay while i was in there since the terminals were a bit ****ty, and it was pretty cheap.

started it up. didnt seem to make a difference sadly. but im gonna test it by taking the truck to work tommorrow. i am bringing one of my 2400 cold cranking amp kinetic batteries i use in my stereo installs incase something happens, ill just jump it off that. but there is litterally nothing left from the OEM set up. so ill be a bit upset if it dies.

 

[seth247]

Sucks man.

I could be wrong but doesn't the PCM regulate the alternator electrical fields through the alt wiring harness. Perhaps a bad connection or possibly bad PCM?

 

[XxxMonoxideChild]

^
not really sure, i thought that was what the voltage regulator thats on the alt does, but really dont know if the ecu itself also has any control?

well, this morning, after having the charger on the battery all night, it read 12.8 volts. drove the 30 min's to work, checked it when i got there, was at 12.4. ok, wasnt too worried. well just came home, and checked it again, and now its at 12.1 volts. so its still going down, but charging enough to keep it running.

obviousely the problem has not been fixed. as i said, the truck has never had issues on these local drive's, just on the longer ones when my g/f drives to chicago on mondays, and thursdays. so any other idea's my friends?

 

[XxxMonoxideChild]

ok, i kinda gave up on anyone knowing what was up with my truck, and started hacking what i could figure out. ive been pouring over my chiltons, and haynes manuals, and differen wiring diagrams trying to get this figured out.

well here's what i did, and what finally fixed my charge system. even though i dont really have an understanding how it fixed it, but owell, as soon as i did it, my volts jumped to 14.7 so thats good enough for me!

connected to the alt, its the engine harness with 3 wires going to a plug, then a single one by itself on another plug (not including the large charge wire obviousely)

well the green wire in the big plug traces back to the charge light in the dash. seems like a sending unit to me. then from there, it leads back to the ignition switch i think. but i tapped a key on 12v to that wire, and as soon as i tested it, my charging system was back into full force! i litterally just did this like 2 minutes ago.


now here's my question? what did i just do? lol. it obviousely works. but id like to know why it works... anyone have more of an understanding of our electrical system that can explain this? possibly bad ignition switch is the cause? thats my only theory i can think of, but really have no clue

:EDIT:

OK, Tested the electrical connections on the ignition switch, and indeed, the wire that should feed that green wire isnt working. hence why i never even got a charge light on, and untill now, didnt even know one existed on the truck. so that was the cause this entire time. bad ignition switch can cause a no charge!! for anyone else, keep this in mind!

 

[seth247]

I beleive that this is the wire that powers the winding that creates the magnetic field through which the alternator windings travel to create current.

I think it's called the "exciter" winding.

If this was not getting full voltage the alt will not create full power. Think you've fixed it buddy

 

[Tbars4]

...The battery cables were both replaced with new cables???...that only leaves your alternator wiring harness...

...This and bench testing pretty much gave you your answers, no???..:scratch: