shorted battery to alternator, now it wont charge

[budwich]

Thanks for the "clarification".... I didn't mean to "upset your cart". Anyways, I think we need to know a bit more about your setup. It was asked but not answered.... how are your batteries hooked up... in parallel with isolator or just in parallel????? Was the old unit always running with the dual batteries as they are??? Lastly... my comment... you are still your own "worst enemy"... running direct connections without "protection".

Last questions, how many wires on your alternator??? My 96 has 5 but the drawings say that the 4.0 is different from others hence the question?

 

[1meanGTA]

they were in parallel with with no isolator, when they were hooked up. the one in the rear was not hooked up when this happened. at one time the stock alternator was charging both batteries, but i did not have the big amplifier installed.

it has one wire from the charging post on the alternator to the fusebox, and a harness with 2 wires going into it. i also have a 1/0 gauge ground to chassis on one of the mounting bolts.

is it possible i just fried something in each alternator from hooking up that connection while the wire was hot? i REALLY dont want to install another alt in here without pinpointing the reason behind these only charging to 11v.

 

[budwich]

hooking up two batteries in parallel without an isolator isn't the "best" idea.... because if one battery has a problem (ie. cell), it will take the other with it as that battery "tries" to maintain 12v on the "power unit".... but that's probably not a problem unless you exceed the rating of the alternator which you could have since you don't know because you don't have fusing in the load path.

Anyways, your wiring is different than mine so I might be off a bit. However, back to my question a few posts back about voltage on leads. Your problems actually appears to be that you need voltage on three leads (two with the key off). If I understand the wiring correctly, ground is provided by the body. Power which get connected thru the starter to the battery, power which get connected to your idiot light (when your key is on), and power which also comes thru your starter to your battery as a regulator input.... this is likely the one that is "fubarred". AND running an alternator without that is usually not good.

 

[1meanGTA]

i know about isolators and the potential problems in not running one, i also know about the voltage drop they create, which is why i skipped it.

as for the unfused wire between the alt and battery, that was one of those things i said "i'll do it later" when i hooked everything up and never got around to.

i didnt realize the starter and alternator were connected in any way, could you elaborate on this?

 

[budwich]

actually, I "mispoke" a bit when I referred to your "starter" as the "starter" is two parts. Basically, your battery isn't connected to a lot of stuff directly.... since the largest wire NEEDS to go to your starter... that's where it goes. A secondary wire goes off to your starter relay.... this is where everything else "picks" up their power... and actually again... just one circuit that goes to your PDB which then is your "mega-connection" / "mega-protection" area AND another circuit that goes to .... you guessed it, your alternator.... thru some fuselinks...)))))))... ain't protection wonderful...)))

So alternator doesn't go to your battery, it goes to your starter. Again, that connection has to deliver "significant" power so big cables... just one though, to one point where another big cable is. Hope that helps.

Anyways, you didn't answer my question about your voltage measurements.... but hopefully if I understand the circuit right (I am a GM man at heart... ), I think that you will find that the "one lead" (actually two) not showing voltage is the route of your problem.... maybe...

 

[1meanGTA]

i did answer. i showed 12v on both sides of the regulator harness with the key in ignition position, engine off. the thicker wire was 12v exactly, the other was about 11.86.

take the key out, and the thicker wire shows 12v constant, the other shows about .01v. this is with the alternator out of the truck and all alt wires disconnected.

 

[budwich]

Thanks... I didn't connect that when you said the 2 had 12 with the key on... didn't connect with the third having twelve.

Just a clarification of the previous post.... when you gave the voltages indications (ie. key on, or key off)... in both cases, the alternator was not connected (ie. all cables were disconnected and you were measuring at the cable ends... right??? It doesn't quite read like that as you make the statement "this is with the alternator out of the truck and all alt wires disconnected." when you talk about the "key off/out" sequence.

 

[1meanGTA]

i know that some explorers do, but mine doesnt have a third alternator regulator harness wire, just the 2 on the outside.

in the first post, when i gave the measurements, which were the same as this time, the alternator was installed, everything except for the regulator harness was plugged in. i unplugged the harness and measured at the end of the wire.

when i just now went and checked, the alternator was not installed in the truck and i tested the ends of the regulator harness again. if need be i can reinstall the alternator, start it, and test the leads while its plugged in.

 

[budwich]

not sure what to say. As you indicated at the start (and now is "clearer"), and Hayes expects, one wire (of the pair) to be 12 with no key.... that's my read on the circuit. You get ~0v on both... doesn't sound good. What I don't understand, is that with key on, you get 12v on both... I would expect one to remain at ~Ov IF the wire has a problem.

something that you may want to try that might help you out is.... put your old alternator in and wire it for "stock".... that is only have wires going to it that are the "originals".... DO NOT connect your 1/0 gauge "stuff" at either the alternator OR the battery (terminal). Start your vehicle up and see what happens (ie. lights, voltage readings, warning lights)... see if anything is unusual (keep your "music" off). Ultimately, I think your problem lies with what they refer to as the "A" side which is the "control voltage" to helps the regulator determine how much "juice" to send to the battery. I think your PDB breaker is "fubarred"... resistive causing a resistive drop towards your regulator which forces the alternator to "work harder" which then eventually causes it to "blow" the regulator / field diode.

 

[1meanGTA]

no i get 12v on one, 0.01 on the other with the key out. 12v on and and 11.86 on the other with the key in ignition position, engine off.

i didnt know there was a breaker in the pdb, all i found was a bunch of fuses, one diode, and a some relays. can you show me what you mean?

 

[budwich]

I am sorry... it must be late... and I can't read.. :-(

Ok oK oK OK (joe pesci style)...

Then, it would appear that the "pair wire" connector is acting as expected. AND since you "shorted" the single "main" output lead, it must be that one that is the problem... duh it was right in my "face" all the time... . In your case, actually you have "three" wires... two stock with fuse links in parallel going to the starter and / or starter relay (I have conflicting circuit diagrams) and a third "custom" wire that you directly to your battery. Maybe your "welding exercise" fried all three in some form... enough so that little or no current is travelling thru. Sounds somewhat unlikely but "welding" does tend to melt things along "low capacity copper" (check at kinks, and connector crimps) which then tend to act like "fuses".
Have you measured the resistance on your 1/0 wire?

My drawings show a breaker / fuse (15 amp) on the "A" side at the PDB. (in 96)

 

[1meanGTA]

well i'm showing 0.7 ohms resistance from the end of the 1/0 wire to the positive battery post, and the same for the smaller stock wire. i show the same resistance when i measure from one of my positive ring terminals right at the battery, to the positive battery post itself, so that seems to be fine. i shouldnt be showing 0 resistance should i, 0.7 is pretty normal?

i really can't think of anything else to check, other than voltage while the engine is actually running and not just in ignition position. i guess im going to put the stock one back on and make sure both sides of that regulator harness show 12v... aside from that it looks like im just gonna put my 240a in when i get it back (with the battery disconnected) and cross my fingers. i'll get it tested before i do this and make sure its outputting 14.4.

 

[manaen]

OK here's a dumb question, did you have your batteries tested? did I miss it somewhere in the post?

Did you have both alternators bench tested?

 

[1meanGTA]

didnt test the battery but i've never had any trouble with either yellow top, and it was working fine about 5 minutes prior to this. got the same thing when i swapped by other yellow top up front.

both alternators were bench tested at advance auto parts and would only charge to 11v.

 

[manaen]

But listen to what you are saying, it was working fine until you shorted it out. A battery test is free from autozone or whatever. Shorting the battery may have fried a cell which would be a good reason your only getting 11v. You've never had a problem until now that is. So test each part of the system individually not as a whole. Make sure the batteries are disconnected. You could also remove them from the car and hook them up to a battery charger to see it they will take a charge. At full charge they should be 12.5v or better.

When nothing makes sense always start from the beginning with the basics, the problem will be logically flushed out. You have already tested all your wiring, and both alternators right? you said your OEM one is not putting out the proper voltage only 11v so that regulator/alternator needs to be rebuilt (i assume you bench tested it, not tested in the car right?), what about the high output alternator, did you have it bench tested to make sure it is still working?

So as I see it you can either continue to beat your head against the wall, or start from the beginning and test each component separately and find the problem.

Shorting out electronics can fry many things actually with the amperage from two batteries your lucky you didn't fry the PCM or sensors, I bet next time you will disconnect the neg batt terminal

Keep us updated and I will offer assistance as much as possible.

 

[1meanGTA]

i used to run and maintain a 6 million dollar binder machine for a living, and now i install 12v accessories in vehicles so i'm pretty good about thinking logically most of the time.

both alternators were tested on a bench at advance auto and showed 11v. the reason i'm led to believe something in the truck (which i obviously would have caused when i shorted the wire to the one) made the stock one do that, is that i only shorted it to the high output alternator's casing. when i put the stock one back in, it did the same thing, charging to 11v.

however, being that i can't find ANYTHING wrong in my truck with my multimeter, all the connections and inputs to the alternator looks normal, i'm forced to HOPE that there might have been some sort of current surge from me hooking up a live wire to my charging post that happened to take out the regulator or a diode or something in both alternators causing them to only charge to 11v. if thats the case, i should be good to go when my 240a comes back from iraggi as long as i unhook the battery. he got it yesterday, so i should know by monday what happened to that alt.

i did check all the fuses and the diode in my PDB. however, i haven't tested any relays. are there any relays that could be relevant?

the yellow top i swapped in to check if i might have taken out a cell in my battery, was not in the vehicle at the time i shorted it, and works just fine in my firebird.

and yes, next time i will definitely disconnect the battery. i would have before taking this job i have now, but i'm learning some bad habits in the interest of getting cars done quickly. i'll also be fusing that 1/0 gauge lead from the battery to the alternator.

 

[1meanGTA]

anyone else have any input? still waiting to hear back from dom about what happened to the alt.