Alternator buzzing when car stopped?

[jpanek]

You said "voltmeter" and didn't specify units on your 0.02 measurement - just to check the obvious, that voltmeter was set to amps (with leads in the correct spot for the meter) and your parasitic draw is then 20 milliamps, right? That is my parasitic draw as well.

A dead battery will kill an alternator (after starting with a jump or trickle charge enough to crank). Running at full charge level for a long time to resurrect a dead battery causes them to overheat. Make sure your batt is at 12.6 volts (fully charged) without a surface charge before you put it in, and get a non-buzzing alternator.

Another thought for you is to look at any ground straps between the engine and frame.

 

[3sacrwd]

Thanks Guys,

Last weekend I took off my ground to my engine, cleaned it up and re-tightened it back to the engine. I took out my starter and re-installed as well to insure no wires were bare or grounding out.

My alt still has a barely perceptible whine to it, and still kills the battery in a day of not driving it. I pulled the battery out of a 91 Landcruiser that was fully charged and hooked that up with jumper cables. The whine was still there in the alt.

I already pulled out each fuse and checked the Alt after each one. It stayed on. The only fuses I have not checked, are the ones behind the dash panel.

What else could it be......:cry

 

[geekinavette]

"buzzing" alternator can only mean bad alternator. Go get your money back (don't forget core charges!) and go get one somewhere else.

 

[3sacrwd]

Thanks for the response....the whining is barely perceptible, if you put your ear within 8 inches of the alt you can hear it.

I wired a 12 V light tester between the neg cable and the battery, and started pulling fuses. The light was pretty bright when I started, I pulled out a 5 amp "LCD" fuse and the light went very dim......Could there be a short somewhere in that circuit????? This would be my 5th or 6th alternator....At least this one is putting out 14.1 volts, so it is at least charging the battery, but the slight whining I think is somehow stealing battery power.....Do you still think I should take it back?
Thanks for the help.

 

[3sacrwd]

OK,

Talked to a Vette Mechanic last week while on vacation in Colorado. He told me to check the wires coming from the alternator to see if there is 12 volts while the key is off......After checking, the Red is hot, and the brown wire is also hot. The middle blue wire is not.

Can anyone else confirm if these wires should be hot at the Key off position??

I would appreciate it if someone else with a similar model could let me know if they have any hot wires coming after the connection at the alternator.

Thanks for the help!!

 

[3sacrwd]

I need some help.......anyone? I am really trying to avoid taking it to the dealer.

 

[Vette_Newb]

Having some experience with alternators, I would say to go get one from a different store and try it. Also, if your having a battery drain it almost has to be shorting somewhere. Get a good alternator from a reputable rebuilder or the dealer.
Most of the time a mass-rebuild alternator is not a good choice on vehicle with alot of electric accessories.

Good luck.

 

[geekinavette]

I wired a 12 V light tester between the neg cable and the battery, and started pulling fuses. The light was pretty bright when I started, I pulled out a 5 amp "LCD" fuse and the light went very dim......Could there be a short somewhere in that circuit?????

Mine has the same problem. If I don't pull that LCD fuse the battery will go dead in about 2 days. The problem is in the memory circuit for the trip odometer, I think. I remember seeing a troubleshooting guide for this circuit...hopefully I can find that again.

Does the "buzz" go away when you pull the LCD fuse?

 

[3sacrwd]

No, the buzz stays on even when ALL fuses are pulled........I even pulled the fuses behind the dash panel.

When I hook up a 12V test light between the neg. battery cable and the battery, the light is bright, when I pull the LCD fuse, the light dims considerably.

Do you have power coming from your Alt. harness in the Key off position?

 

[LittleRedFlatBack]

I'll check the power to the harness wires to the alternator (key off position) when I get home from work if you haven't gotten your information by then.

Dennis

 

[LittleRedFlatBack]

I guess my 90' model is a little different, but here's what I found with the key off. The red (8 gauge) is hot, the brown (12 gauge) is not and the brown w/red stripe) is not. I hope this helps.

Dennis

 

[3sacrwd]

Thanks for the bad news...ha, ha. Looks like I probably have a short that is causing the current to run backwards to the alt....Guess I will have to find out what the brown wire runs and go from there........anyone else with a model year closer to mine, please help me out and check your wires as well.......just to be sure.

Thanks for your help.

 

[Galen]

Unhook the wires from the alternator and see if the whine stops. I would bet on a alternator problem. The regulator and everything is in the alternator. There is only 1 wire that is switched and it is very small gauge and plugs in, unlug that first if that stops the whine it is a switching circuit. If that makes no difference it is in the alternator causing the draw. The large red wire goes to the batt unswitched it uses diodes in the alternator to allow one way flow of power. The brown could be a power tap going to something else and picking up power from the red wire. Let me know what stops the whine and I will look at the wiring schematics.

Galen

 

[3sacrwd]

Thanks Galen,

The bracket clip holds 3 wires coming out of the alt. 1. Red, 2. Blue,3. Brown. The Red and Brown wire have 12V. with the Key off..........All have power with the car started.

When I unplug the entire clip, the alt whine does stop, and the battery does not drain down. Only when I plug the clip back in does it start to whine again. This is my 6th alternator, but I did not get the AC Delco factory replacement, I went with the AutoZone cheapo....That was before I knew any better.......This problem has been ongoing for almost 10 months.
Thanks for the help

 

[LittleRedFlatBack]

3sacrwd

Just a quick note about the current test I did. When checking for "hot" wires to the alternator, I unplugged the harness connector from the alternator and used a test light inside the plug. I guess if the alternator completed the circuit, I might have given you some bad information. Hope this helps. Good luck with the problem.

Dennis

 

[3sacrwd]

Thanks Dennis,

When I checked my harness with the key off, I disconnected the harness from the alt and tested the wire end, not the alt end. I had current from the wire end......when I tested with the car started, I probed the wires with the harness connected.

So, your red wire is hot, the other two are not.....I have the red hot, and another wire hot....I think somehow that is my problem.

If anyone has more comparisions, I would appreciate it, and if anyone can tell me what the brown wire controls, that would be helpful too. Not sure if the schematic in my Haynes manual will have that or not, I will have to research this weekend.

Thanks for the info.

 

[vettenick]

I'm assuming you mean .020 amps? If that's what you mean,then that type of draw is OK. If you measured in volts, all you did was measure the voltage drop between the cable and the battery, which really doesn't help you.

 

[geekinavette]

This is from the '84 shop manual, but I would imagine '87 is very similar:

The brown wire provides the "field" voltage for the rotor windings, and should be hot only in RUN, the other two red ones hot all the time. The studded red wire is the main output, and the red one in the 2-wire connector is the "sense" voltage for the regulator.

The brown wire should be to the left as viewed from the backside of the alternator.

The shop manual does mention that that "resistance wire" is to protect the diode trio (current-limiting). It might be worthwile to check the resistance from the battery + to the brown wire at the alternator, with the 2-wire connector (brn and red) disconnected and the ign. switch in RUN and make sure you have that 10 ohms of resistance.

Bill

 

[3sacrwd]

Thanks for the schematic. I have a red, brown and blue wire coming from the alt. connector. The red and brown wires are hot....Not sure if that is supposed to be like that or not.

 

[geekinavette]

Look at the wire position in the connector...I wouldn't think that would change.

The "left" wire (as viewed from backside of alternator) would be hot only with ignition in the "RUN" position (blue?), the right one would be hot all the time (brown?) as would the studded connection (red?)