i have a charging issue with my 1996 Z28 M6. the battery is literally getting killed while the car idles. when i rev the voltage jumps right up to normal. at idle it just creeps slowly down into the red until finally there isnt enough voltage to keep the car running and it dies. if i shut the car down forget it, its dead and wont restart. there are 3 oddities that ive noticed that will hopefully clue someone in that will be able to help me. the check guages light NEVER goes on, even when its deep in the red. when my last alternator died it was on all the time. the ABS INOP light is on and wont shut off, even after driving. also, the LOW TRAC light flickers on and off. its not my alternator, its brand new. its not my stereo stuff, its disconnected. and this is the 2nd perfectly fine brand new battery thats been killed. this literally appeared out of nowhere and has me baffled. any ideas??
thanks
brian

 

Have you checked all the grounds? A long time ago I had an Iroc that I changed the battery and alternator and still had charging problems and cooking alternators...turned out to be corroded grounds. Definately worth checking out. Do you have underdrive pulleys? A large stereo?

 

have you checked the output of the alt????(Should read atleast 13.3 or better at the battery with the car running at idle) Have you checked the voltage of the battery??? ( New batt should be atleast 12.0 or higher) Some new batts can be bad, and with the cold now it can play havack...It could have a bad cell.....

93Z Will

 

Not the alternator? I think it is. Even new ones can be bad. Have it load tested. Sounds like the voltage regulator in it is not working properly or you have a serious load on the system.

 

guessing either your grounding out, bad battery, or bad alt. the fact that you said it gets really low at idle, but comes up when you rev it makes me lean towards the alt.

 

It also would depend on whether you have an crank pulley that's spinning the acces. belt too slow. At idle, the alternator may be spinning to slow to get a decent charge.

 

my vote is bad alt, and/or a bad battery. more likely bad alt.

 

i HAD a big stereo but have disconnected it, its been over 2 months and the problem started 1 month or so ago. the battery is dead at this point, fully dischared and will be the 2nd ive been through brand new, so its something thats not the battery killing it. the alternator when revved perks right up to normal range, almost like its passing right through the battery since its dead. i have a 2 piece underdrive setup, underdriving the crank and overdriving the alternator to compensate for the general underdrive from the crank pulley. where can i get it load tested? i mean i cant shut the car off if im out or itll be dead.
thanks
brian

 

UPDATE! well my buddy and i tried to figure out WTF is wrong today since it was 55 degrees. we checked all fuses, nothing wrong. jumped the car and it started up, voltage read real low but i kept a solid 1000 rpms idle at it was reading like 3/4 of the way up. then out of nowhere all the weird gauge lights that were on went away. so i take the parking brake off and BOOM, ABS inop and low trac light on again. took it for a whip and the ABS light was on still. got back and put the brake on and after a few secs the ABS light was gone! then put it down and on again. also, the voltage after the driving and idling the voltage was right above the red and holding steady. so i put her away and shut her off. and she restarted after i shut her off! usually shes DEAD. so i did it again and she started. the voltage read lower both times. so now im letting it sit for a bit and then ill try and see if theres any juice left. what do you guys think? i could really use a hand since warm weather appears to be around the corner.......
brian

 

If you can get it to Autozone, they will do a free battery, alternator, and start test. However, if the battery is weak, the test will finish killing it, possibly leaving you stranded in the parking lot. So be prepared for that if you go there.

 

Hmm...kill your battery and they just happen to have new batteries in the store. Clever.

I think your alt is just not charging well at low rpms. I would try another one. If it contiues to read in the red long enough, eventually your battery will discharge enough reserve power to where you cannot start the car.
Low voltage will make the lights for the ABS, Air Bag, etc. act up.

 

I'll go with the alternator. Sounds like the regulator is not producing enough "on" cycle at low RPM. Rotor field current is variable and should be 90% on and 10% off at high electrical demand of low RPM to control the average for proper system voltage. As stated before, have it load checked at Autozone or a similar parts outlet.

 

The Autozone test equipment puts a heavy load on the battery and charging system. I don't know what the load is, but when I worked there, I saw many "suspicious" batteries bite the dust. When I say "suspicious", I mean they were already the prime suspect in no starts, and no charge situations. I always warned people that could happen, and let them make the decision. Of course the battery and alternator can be removed and taken in for testing. Of course we sold a lot of batteries that way. But they needed one anyway.

 

thanks for the help guys, ill look into it getting load tested, today seemed semi-promising.......one thing i never mentione is it FEELS like the ABS is working fine......
brian

 

UPDATE #2!
well, after sitting for a week the car started up, which was a total shocker. however, after a few minutes of idling the car just died, i heard it die, went outside and the batterys dead. do you all think that the alternator at idle just cant keep the juice up for some reason? i still get the ABS inop light on when the parking break is down, yet it goes away when its up. just weird i guess. any ideas?? seemed like things were finally looking up, until it stalled while idling.
brian