Well.. the reason I agree that this is a problem that certain conditions need to be met is because.. ok.. listen this all started with me being under the car and noticing that the alternator has some kind of "hum/whine" thats so insanely faint that you practically have to have your ear to it or at least in the right position over top of the engine to hear it. But when you do hear it, its clear as day. Its a constant, unending "beep"

I think the inherent problem with these draw tests is that.. when i go to put the multimeter in series with the battery, disconnecting the negative terminal makes the sound stop. Disconnecting the positive terminal, makes the sound stop. Disconnecting the excitor wire makes the sound stop, disconnecting the ground terminal makes the sound stop. So the problem, in my amateur opinion.. is that trying to seek out the issue using the multimeter makes the problem stop. I can only recreate the problem by fully starting the car then turning it off but leaving everything connected.

Now obviously I cant START and turn off the car with the multimeter in place... So I think Im running to a stop here and not making any progress on the real issue.

I have done extensive searches on this issue and the threads always end before any real resolution occurs.

alternator humming - LS1TECH
^^ this is another guy with the same problem, no resolution.


"ell i dont know what to do then...say some how it is putting the car into a slight Key On Engine Off (KEOE). How do i fix that or what els can it be that the ALT is doing that. It is the ALT making that sound i know and it does go off when i disconnect the clip in pulg on the bottom of the ALT and when i disconnect the battery. But i do have an other ? what color is the wire that runs from behind the motor with all the other wires that connects to the clip plug on the bottom of the ALT. The guy that had the car before me messed with alot of wires on the car like the fans the lights the wires under the steering wheel of the car the ALT and compressor wires and some wires with the ac because when i turn on the ac to see if it works smoke came out and it smelled like bernd wires. I have no idea what this guy was thinking before me that owned the car."


Alternator Whine when car off! - Third Generation F-Body Message Boards

another one related to a third gen but a bit different situation.

"When ever i turn my car off i can pop my hood and put my ear to the alt. and i hear a whining/humming noise. If i dont unplug the connnection at the top of my alt. at night, when i get up in the morning my battery will be dead as a hell. If i do unplug it in the mornings when i try and crank it, it clicks every time, about 5-10 times before it cranks. If i hook jumper cables up to another car it starts right up, no problem what so ever.

Now when i first crank it up in the morning when its cold the alt. has a good strong charge at about 13.8-14.4v. After about 10 minutes the alt. gets real hot and the volts. vary from 12-14.0v. Plus when im turn my lights, heater, or fan (manual fan) on the volts drop real low, then fluctuate at about 10-14 volts. I had my alt. checked (its 1year old) and its fine. My battery is 2 months old and my connections are new. The thing that has me baffeled is that the connection i disconnnect at the top of the alt. (91' TA LB9)
is the 12v wire and neg. that control the fans. Alot more info is availible if you have any questions or might now whats wrong."

97 Cavalier - Alternator hum with engine off - Third Generation Forum - j-body.org - The J-Body Organization

"1997 cavalier. The alternator is making a high pitch electrical sound (you have to put you ear up to it to hear it) after the engine is turned off. Along with the hum it has 4.96 volts at the alt. plug. After pulling the PCM fuse it stopped. The 4.96 volts at the alt plug stopped also. I put the fuse back in and 0.0 volts and no sound. Restart the engine, the alt charges. Shut it off, and the sound is there, unplug the alt plug and have 4.96 volts. I'm thinking a relay is stuck but I'm not sure where to find it to check it . Any Ideas ? Thanks all."

GM alternator hum... | IH8MUD Forum

"Noticed a buzz / hum coming from my GM alternator this weekend when everything is turned off. It is very subtle and never noticed it before. Thought maybe it was there all along and did not pay any attention to it. Well, went to start the rig after sitting for a couple of days and the battery is dead. Now, I went through some of the wiring this weekend and just zip tied, cleaned up stuff, etc...so I don't think it has anything to do with me messing around. I also researched the hum here on mud and found a couple of items but nothing conclusive. It is a rebuild GM alternator from O'Reilly with an internal volt reg (I think), but looks brand spanky new. Before I go swapping it out, any ideas on this? Wish there were s a 350 / SBC / GM sub-forum so I would not need to keep bugging this section with Chevota crap. Thanks for any help."

Another different type of car having this problem.

These guys all say that it drains their battery in a day. Everyone says internal alternator short, but Ive tried 3 alternators. My stock one, a rebuilt stock one, and a 145amp truck alternator. It does it with my original excitor, and i bought a new one and it does it with that too.

My voltage is absolutely fine with the car running, does nothing strange. The car only dies when its off.

Im really lost here because seeing the high(ish) draw had me thinking maybe eliminating that would make the sound go away. But Ive disconnected nearly everything in the car that can possibly be disconnected.

Like just now, every connector under the driver side dash has been disconnected with no drop in amps. Its actually at 0.168 this morning instead of 0.158. Oh and Ive had the bulb for the glove box light removed for months now so as to eliminate that possibility.

 

buzzing noise from alternator w/key off - ChevyTalk - FREE Restoration and Repair Help for your Chevrolet

"hello,
my name is sal. I have a 77 chevy blazer with a 454
out of a 89 silverado. The problem is a buzzing sound
coming from the alternator with the key off. the alternator is a three wire, the bat. and a connector with a brown wire and red wire. the only way the noise goes away is when i disconnect the red wire from the connector. does anybody have an idea what is causing this buzz and why it only goes away when i disconnect the red cable......sorry for the long post "

alternator works great but hums when ignition is off | The H.A.M.B.

"hi everyone, does anybody know what is wrong with my charging system? i have a brand new alternator meant for a 1991 chevy silverado on my 1991 350 SBC, its in my 1953 chevy 3800, it charges great, battery reads 14.5 v when engine is running, but when the engine is off i can hear a faint electric hum coming from the front of the alternator. if i unplug the BAT of coarse it turns off but it wasent doing this untill i ran the Lamp wire to a power source on the fuse box, (i diddent have a idiot light, & it wasent charging unless i had power to this wire) there is too other wires that i read were not important, & were meant for the ECU when the engine was in the 91. does anybody know what is causing this? i am worried that the electricle leak will drain my battery if i leave it for a coupple days, and is this wire not ment to have that much power to it?"

Alternator "buzzing" or "humming" when car is off, battery dies

"Wondering if anybody has experienced this one.

Background: 1996 LT1, factory harness reworked by Speartech. I finally got my LT1 running and took the car for a spin around the block. Frickin' sweet!!

Instead of disconnecting the battery cables like I usually did durning the project build, I figured I'd leave everything connected. (this is how I will usually "store" the car for a week or two at a time) The following Saturday I put the keys in... nothing... dead battery.

Well, long story short, my faithful Optima red-top gave up the ghost after 6 hard years. So I bought a new one, installed it, everything worked great... until I came out to the garage the next morning. I heard a faint buzzing or humming... lifted the hood, and the sound is coming straight from the alternator. Sounds like the voltage regulator is buzzing. So I disconnected the plug that goes to the alternator... buzzing stops. Take my multimeter after it... sure enough, I'm getting voltage feeding from one of the wires to the alternator.

Is the alternator supposed to get voltage when the car is off? Is this a case of Speartech wiring it up to a constant hot versus a switched hot by accident? Yeah yeah, I'm going to call them, but I wanted to get educated before I go pointing fingers on who is to blame.

Oh, and the alt. checks out OK according to the factory troubleshooting guide."

Should the alternator "hum" with key on and engine off? - Third Generation F-Body Message Boards

"Like the topic says. I noticed in the garage when its quiet that if i turn the key on and the engine is off i can hear the alternator "humming". I verified that the sound is from the alt. It seems to be charging alright, i was just concerned about the "humming". Any thoughts?"

Theres more examples I can show you.. but not a single definitive answer in ANY of these threads. LOL

 

This is (what seems to me) the best answer I can find:

"Buzzing noise when it is off indicates the field is still being supplied current from the battery. Not good, but not the alternators fault because the alternator gets field current via the ignition switch. You might have a defective ignition switch."

Do you think theres any plausibility to this?

Reason I say this, is because when the noise is present and I pull the Ignition fuse or the ignition relay.. the sound stops. I tried replacing the relay and fuse and both those things didnt solve the issue. Im gonna try the switch next.

 

The manual should state what wire has what power going to it. You should be able to work back from there.

Back in the day Chevy sold Geo line of cars and the manual sucked. In many case the electrical area where just plain wrong. In those cases I would grab a working car and compare voltages and work my way back. Do you have access to a working GM car? Its the 3 wire system I think?

Normally I would say an odd situation like this is a failed ground causing the power to back feed through another component but if you have been re-pinning connectors who knows. Most of time when people explain complicated and odd electrical problems I stop listening about a minute into it because I know it will end up being a ground. You can spend 10 hours with diagrams trying to figure out how all of it is related or you spend 15 minutes running ground jumpers everywhere you can think and the issue goes away. Then remove them one at a time until it comes back.

 

hmm.. ok well i will be honest, thats been nagging at me since this whole thing started. now, im unfamiliar with jumping grounds. can you explain this process to me a bit? like a quick how to? i can give that a shot before trying anything else and see where it gets me.

 

I use this one. It works great.
Make sure to get a meter that has DC current measurement. The cheaper ones and some more expensive ones do not.

 

Primary grounds are Battery to engine and Battery to body. Next you have a PCM ground which on the 3800 and the LT1 are on the passenger side of the motor (sorry I have not done much work on my LS1 yet). There should be a dash ground to the body. I am sure there are several others. The fear is that a resistance has built up under the ground so we would run second jumper wires near the original, back in the day I had a dozen jumpers varying in length. Jumpers are just wire with alligator clips on them. We would focus on the areas that had the issue but it never failed when we called tech support they had us add more or at least have us move some around.

If you recently installed this motor is there any chance you could have a ground disconnected?

 

Yes it is possible, only human and all lol. I did pay attention to making sure the grounds were all connected like the ones on the back of the driver side cylinder head, the one below the coolant temp sensor/below the first spark plug that is on the block just above the line for the oil pan, then the one on the body next to the starter, but there is one i wanted to ask about.

It is one that connects to the frame just below the ABS block. It is a braided ground strap. Well the guy I bought the engine from tore it RIGHT BEFORE the end that gets bolted to the frame. I am not sure if this is acceptable.. but I soldered the torn end with this big chunk of solder surrounding the braided strap. He also tore the oil level sensor pigtail, the crank position sensor(tucked in behind the starter), and some of the starter wires like the purple one, but I fixed those as well.

Now the braided one that connects to the frame below the abs block, that one is part of the wiring that goes to the O2 sensor on the driver side, and the ground wire on the engine block below cylinder 1 spark plug, and the alternator excitor wire plug. Do you think this might be lending to my problem?

I wasnt sure how exactly to fix a braided copper ground strap like that, and even if I got a new one, how would I go about replacing it? This braided strap goes into the wiring harness and disappears in the mess of wires.

Would it have been better for me, instead of soldering it back together like that, to remove the circle end and replace it BEFORE the soldered section? I dont have any pictures but in the morning when I get home, Ill snap a pic and show you what I mean.

http://www.fl1v.org/ls1/g109.gif

Look at that picture, just imagine that right before the connector to the frame, it is broken and soldered back together with a quarter size hunk of solder. I know its ghetto, but I wasnt really sure what else to do and didnt find any decent info on whether or not this was acceptable.

 

As long as the solder flowed around the strands and cooled down to ambient temperature without any cooling aid, such as blowing on it, and solder does not look like a ball making for a cold solder joint, it should be good.

You can always take a 10 or 12 AWG wire, crimp terminals onto the wire, and use it for a ground wire.

 

Im going to clean up all the grounds and maybe replacing all the battery to starter/alternator/fuse box cables and see what happens. Ill report back.

Thanks for the help guys. I have a renewed commitment to seeing this problem through. Im off in the morning and Ill be tinkering with it all weekend so Ill update soon.