I was driving today and when I was on the freeway I noticed that the check engine light started to flicker on and i started to intermittently lose power. I noticed my voltmeter was only showing about 8 volts. I pulled over and when I started looking under the hood I started seeing sparks from my alternator ground strap swinging and grounding itself on anything metal it found.

I then pulled the negative terminal off the battery, but in that proccess I melted part of the connector (when I pulled it off it smoked like crazy and at one point the cable fused itself to the battery terminal).

I was just working on the P/S pulley bracket and took off the groundstrap (that goes from battery to engine) and then put it back on. I think my main groundstrap might have not made a good connection or something and then the entire electrical system tried to ground through just the ground on the alternator because the other ground wasn't grounding.. and then the screw that the alternator ground strap mounting too got so hot it melted off.

The alternator is about 1 month old. It's a lifetime warranty. So, I'll take it back tommorow.

If I replace the groundstrap/replace the alternator/replace the battery I am hoping this will be fixed.. any suggestions? What do you think happened? Is there a better spot to ground the battery? Can I use two ground cables just to be safe? I need my car to go to work on tuesday so any help would be appreciated.

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89GTA5spd – Engine: Stock G92 LB9 w/AFPR, JET Fan Switch, Air Foil, Ported Plenum, T.B Coolant by-pass, 180 T-Stat, Flowmaster 3” Cat-back – Transmission: Stock WC T-5, Suspension: Alston SFC’s, Hotchkis STB, Eibach Pro-Kit, 255 BFG Comp T/A’s – Power Adders: Paxton SN2000 w/ MSD BTM & water injection, NOS TPI #5151 Kit-- Interior/Stereo: Autometer Phantom guages, Sony Deck, RF Subs, Orion amp – Times: (Stock) 1/8 9.78 sec w/ 2.42 sec 60ft, no times w/ S/C or N20 (yet.. )

 

Yes,you about summed it up and there is no reason you can't run two grounds to be safe.

 

I do not understand your post.

You stated I have never heard of an "alternator ground strap". I do not understand how a wire at ground potential (the alternator "ground strap") can conduct electricity when connected to a conductor at the same potential (ground). Since the alternator case is ground, and the alternator is mounted to the engine (through metal brackets/bolts), all exposed metal should be ground.

I am not aware of any ground wires or terminals externally connected to a CS-130 alternator (what third generation F-bodies use). The alternator case for most alternators is ground, which is then grounded to the engine through the mounting brackets/bolts from the factory. Normally, there are no external wires to ground an alternator.

Perhaps I should ask what kind of vehicle/year/alternator you have, as well as any modifications it received.

 

On the alternator there are two connections.

1. A two wire weatherpack connector that snaps in

2. A somewhat thick (perhaps 10guage) black cable that goes from a post on the alternator to the black cable on the battery.
What I called a ground strap.

I don't see how that's confusing.

My car/modifacations are listed in my signature above, the alternator is a stock replacement (105 amp alt if I remember correctly) and I am sure that other people on this board have the same stock setup. (two connections/3 wires).

I am going to look at it today.. I am going to double up on the ground straps now I think.


[This message has been edited by 89GTA5spd (edited May 21, 2001).]

 

I just pulled the alternator off. The negative cable attatching to it looked like it had a lot of heat going through it. The post is completely seperated from the alternator. The funny thing is that the main ground cable (cable from negative battery terminal to engine block) was on SOLID. That sucker wasn't moving. Could it be something else? I didn't have the little washer in, because it wouldn't fit when I put the ground strap on, but the strap was on the block so tight i figured it would be fine. I'll put the washer back on when I put it all back together.

I had the ground cable mounted to the engine on the same bracket that I had my alternator mounted to.. I am almost positive that that would cause no problems.

Could it just have been a faulty alternator? This wouldn't be the first. In the 2 years I've owned my car I have gone this is my 5th alternator... (4 were under warranty ) This one is a lifetime warranty autolite re-build. I had really bad luck with the exide re-builds (2 had bad voltage regulators out of the box).

Please help me out if you can.. I need this car for work and school.. I work at an oceanography insitute and my boss gets upset when my "race car" has problems and i am late/miss work.

 

It is/was confusing to me because you stated:

What you called a "ground strap" is by no means "ground" nor a "strap". A ground strap is usually a braided wire (as opposed to a stranded or solid wire, insulated or uninsulated), typically found connecting the engine block (ground) to the chassis and/or frame (again, ground) or frame to frame.

The wire you are referring to is a wire which is positive 12VDC, connecting the output of the alternator to the battery positive terminal.

While I suspected it was an 89GTA (as in your signature), since you did not specifically say so in your text, I could not presume the problem you were describing was for the same vehicle.

Additionally, the title of the post you made was: The confusion (at least to me) is because a "negative terminal" on the alternator does not exist.

Understanding that the terminology you are using is not correct (there is no negative cable/wire/terminal/ground strap on the alternator - a positive wire/terminal/post/stud - yes), it appears that the alternator was outputting excessive current which caused the positive alternator post to separate (melt).

EDITED PORTION:
Since you originally stated that the alternator (positive) output wire was shorting to ground, this is probably the most likely source of the alternator output stud melting from its plastic base. With the output directly shorted to ground, that would easily explain the why. You'll have to replace the output cable. GM used 8 gauge in my 1991, along with enclosing it in a wire loom for further protection. In 1991, GM only used a fusible link for the alternator output to the battery terminal (via a junction block) for V8 VIN E (5.0 TBI). All others (V6 VIN T, V8 VIN F and 8) did not use a fusible link although they all went through a junction block or molded juction just before the battery. If you can't find any 8 gauge wire, use 4 gauge (probably better) or use two pieces of 10 gauge wire in parallel.

[This message has been edited by Stuart Moss (edited May 21, 2001).]

 

Thanks Stuart.. your right, my nomenclature was incorrect.

I was thinking about it after I posted and it seemed redundant to have a ground on the alternator. I assumed it was a ground because of the black color of the cable and I traced the cable incorrectly to the negative battery terminal.

I think it wasn't a ground problem now, but rather what you said about a short. I am going to replace it, and _not_ add a ground strap but just clean the mounting surfaces and the strap on mine now. The cover on the positive post of the alternator had come loose and maybe it shorted by touching something.

I still am not sure why so much power was trying to go to through the negative terminal of the battery when I removed the terminal. That is what is scaring me now. Normally you get a spark or two... but when I took it off it was going crazy and partially melted the terminal. Maybe it was just the alternator power wire again. I'll post if I get it working. I need to catch a ride from one of my roomates to the local kragen.

 

Just a guess, but perhaps when you tried to remove the negative battery cable, the positive wire from the alternator to the battery positive terminal was at that moment being shorted to ground. That I would guess would easily cause over 100 amperes (300-500? - whatever the battery capacity is...) being passed through that negative cable that you are now trying to remove.

With that much current being passed through a wire you are removing, the resultant arc would easily explain the fireworks.

[This message has been edited by Stuart Moss (edited May 21, 2001).]

 

I think that's what happened, when I was removing the battery lead the alternator + cable was swinging around. The whole fiasco makes more sense with that cable on the alternator being positive.

What are the chances I fried a bunch of my sensors or computer? I guess I'll find out. I wonder what Kragen will say when I come in with an alternator with no post on it.

 

Well, I replaced the alternator. I noticed that the ground cable terminal was maybe 1/8" away from touching the alternator body. I moved the ground strap to a different spot after cleaning it and sanding it as well as cleaning the new spot on the block. I then made sure that the positive terminal on the battery was completely covered and then taped over it w/ electrical tape just to be sure. I didn't even have to replace the battery (or charge it). It fired up first time.

The car seems to run fine too, I guess I didn't fry anything. Oh well, glad that is over (hopefully). It kinda sucked not having a car.