98 LS1

So Ive been having a pretty consistent battery drain lately. Initially I thought it was my 5 year old optima red top and so I went and got a new battery. Well problem is still there.. sitting anything over about 5 hours and the car is dead. I looked up the ericthecarguy video for parasitic drain and gave that process a shot. My multimeter on DC 10amps reads 0.09 with it in series off the negative battery terminal. This means Im getting 90 milliamps drain? He states in the video that 50 milliamps is the acceptable amount. I went over to the fuse box and I heard an extremely faint hum coming from the alternator. I unplugged the harness pigtail and the sound went away. Google search turned up a few threads where people had this problem and the consensus was that the alternator was going out due to an internal part failure. I figured that this must be the problem and bought a replacement.. (whether this solved the problem or not.. I just bought an lm7 and im getting ANOTHER ls1 this weekend but none with accessories so I didnt mind picking up an extra alternator) I installed it today and at first I did NOT hear the hum. I took my old alternator back to the auto parts store to be tested and it tested GOOD. Well.. I got home and went to listen for that hum and dont you know its still there.

Am I crazy or is this NOT normal behavior for an alternator? The car runs fine so long as the battery is charged well enough to turn the engine over. Once its running its fine.

This hum is extremely faint. Its like the sound you hear from a car battery charger when you have it hooked up to a battery. Its almost unnoticeable but when you put your ear right up to the alternator you can hear it clear as day. Two known good alternators are both doing it.

I ran out of time today before I had to get some sleep before work but I am going to do the test again and pull fuses. Do you think its the pigtail? I have also recently put in glow gages and a pioneer aftermarket radio here recently.. I pulled the wiring from the glow gage when I first noticed this issue thinking that might be it but Im guessing its not. Havent pulled the radio yet. There are no obvious signs inside the car like lights stuck or left on, doors left open, etc etc.

Have any of you ever experienced an issue like this before?

 

I have. The alternator was making more of a high pitched whine though, not a hum. Mine was a bad alternator, had bad diode(s). For lack of a better description, the diodes act like an electrical gate valve. A bad diode can cause a parasitic drain. Not saying yours is doing this, two bad alternators would be a coincidence but not impossible. When you disconnect/reconnect your battery cable, do you get a hefty spark as if there is a draw on the system? For starters, you would probably want to start by pulling one fuse at a time and see (listen) if the alternator stops humming a tune.

 

Yes! Its a hum but when i get close to it i can hear this very high pitched whine.. almost like a constant beep sound. I did the draw test in the engine bay but havent done it in the cab. voltmeter read 0.09 no matter what fuse/relay i pulled. i did not check to see if the hum/whine went away though. Ill go ahead and redo it and listen for the sound. thanks for the suggestion

edit oh and yes, the cables spark but it seems rather mild. like i can hear the popping but sometimes i dont even see a spark

 

Before you do anything,
set up voltmeter as ammeter on battery cable,
90 mils in place, humming/beeping in place of alt,
Now unplug/disconnect from alt.
If amperage goes down, beeping stops, bad alt, period, or at least internal regulator is faulty.
If beeping still there, then remove red lead on BATT stud.
Amperage gone, bad alt. Try a different store for a different batch/brand of alt.

Once problem found and repaired, wire brush both battery pad and battery cable for removing the carbon arcs as they will present extra resistance in the connection of cable to battery.

 

ok so update. i put the voltmeter at DC10A and noticed the buzzing on the alternator was not there. so i had the negative cable on the battery disconnected, positive on voltmeter set to DC 10 amps, negative on the negative terminal. buzzing went away.

So i plugged the battery back in, still no buzzing. I went inside the car, opened the door, still no buzzing. I engage the key on, engine off, buzzing is BACK. So i pulled key out, buzzing still there, started pulling fuses. Pulled an entire box, then started the second one and when I got to Eng Sen 20 amp fuse, the buzzing STOPPED.

Im going to try your test everett, but would this indicate that one of my engine sensors is causing a drain on the alternator?

edit: only codes i get are EGR and AIR codes since they are deleted.. if it matters at all

 

so i went through and disconnected the sensors that eng sen fuse controls and no dice, still the same. then i went back and unplugged that fuse again and couldnt replicate the problem. i may have been mistaken about that.

 

ok everett.. i did your test.. i think i may have it confused. no drop. however let me explain what i did and you tell me if i did it right or wrong. disconnecting the battery to put the voltmeter in series with it STOPS the beep/hum thing. its not until i have battery connected, engage the car from inside the cabin with the key to car on engine off, that the beeping begins. then i disengage key, close door, all power shuts off shortly thereafter but the beeping continues. if i were to engage the key like that with the voltmeter in series, wouldnt it go boom?

so what i did is just like the parasitic draw test. dc10amps setting, positive voltmeter cable on negative battery cable, negative voltmeter cable on negative terminal. registers 0.09, then i disconnected the harness wire. checked, no change. disconnected red batt stud wire near the fuse boxes and reading dropped to 0. obviously didnt touch the ground on the back of the alternator with the battery basically still on, lest sparks fly.

did i do it wrong? does this check out? damnit i wish i understood electronics better.

edit: and so while im still trying to wrap my head around this whole thing.. i decided to finish off the regular draw test with the ones in the cabin. Power Accessory 15 amp fuse causes the .009 to drop to .005. also the gauges sweep upon unplugging and plugging it back in. I have my glow gauges wired to that small ACCY slot in the interior fuse panel. is this the additional source of draw? are my glow gages causing the problem?

 

Possible, if they're LED's. If they are, have you checked in the dark to see if the lights are slightly glowing when "off"? Sometimes, depending on application and the LED's themselves, a resistor wired in series is needed to make them go completely out.

 

Voltmeter is fused, at least the better brands are, but yes cheaper brands are not fused and one gets to see how much smoke manf packed into it.

Your parasitic draw test proves alt has a leaky semiconductor, 90 to 0 with red lead unhooked.

ACCY terminal should not have power with ign switch off.

 

the glow gauges are wired through an inverter first, then to the accy slot. also, via that inverter.. i turn the glowing aspect of everything off after running the car and i can see my leds in the holes for the pins turn off.

this alternator thing though, wouldnt removing that red lead by the fuse box essentially be removing the positive wire from the battery, just in a different location than the actual positive terminal on the battery? then wouldnt it stand to reason that dropping from 90 to 0 would make sense? as power from the battery would stop and the voltmeter would be reading only from the negative terminal?

im going to return this one, throw my stocker delphi one back in and get a better quality one. ive been keeping my spare battery and battery charger with me everywhere so i dont get stuck anymore.