Xgpnavsys

Hey guys, I'm currently driving a 1988 bright red coupe and my car happened to die when I parked it. I put a new battery and alternator in it TWICE. My worst problem is the voltage has never been above 11.6 since replacing the parts and I can't get the alternator to recharge the battery since all the battery does is run untill it doesn't have the juice to crank the starter. Any ideas for me? My feeling is a ground or a contact somewhere needs to be replaced. I refinished the positive size contacts for the alternator and the alternator grounding points on the brackets themselves. No change whatsoever. Also at idle the cars voltage is higher than at running(Less load, Duh.) but, under light throttle the battery recharges and the voltage goes up a tiny bit so I have some connection somewhere. However, under heavy throttle the battery loses juice. Should my next step be the plug in module on the negative side of the alternator?

Da Mail Man

......1st, if you plan on keeping the car, you NEED to get a HELMS service manual...next, get the alternator TESTED at the time you buy one and at this point you need to have yours tested....take a volt meter and with the car off, touch a probe (i am sure you know which one goes where) to the wire at the back of the alternator to ground..you should have 12vdc..next, get the car started in some way and do the same....you should have 13.5+vdc or better......if you have no voltage in the first step, you most likely have a blown fuse link or bad connection on the battery....in the second step, if you don't have this voltage as above, then the alternator is bad......while doing the testing in both cases, wiggle the wires around a bit as far back as you can as this will hopefully locate a broken wire inside the insulation....

AGENT 86

Time for a little more diagnosis
http://members.shaw.ca/agent86/Charging%20System.pdf

Da Mail Man

........

65Z01

I tend to agree that there is either an open between the alt & batt or the alt is defective.

xflagz51

One other thing, don't even think about using cheap Autozone/Pep Boys rebuilt alternators. That is usually everbodies first mistake, most of us have shops pretty close by that will rebuild alternators and do a heck of a lot better job than these mass rebuild houses. Make sure that your battery is charged up fully, if it isn't then you are overworking the alternator and that will kill the 105 amp small alternator that you have in your car.

williammackean

Bright red cars tend to have this problem.

I also suggest a Optima battery. They hold a charge like no one's buisness. I don't even use a battery tender in the 6 month storage period.

RandyJ75

I would disagree about the Optima battery. I had one for a year and a half, and it was a POS. It finally died, and I took it back to Autozone and got a Duralast, which has been much better.

coupeguy2001

try tightening the alternator drive pulley. I had gotten a rebuilt from autozone that the pulley was still spinning, but the alternator was slowing down because the pulley nut wasn't as tight as it was supposed to be.

Xgpnavsys

Guys I gotta say thanks. First all three (including the original) were still good. The first battery had a damaged cell and I replaced it again and holding about 11.7 solid with car running. The alternator is sending the current back its just not making it to the battery. Its an AC Delco rebuild out of mexico and according to the alternator tester at Kohlweiss they were good. According to my mechanic, (I gave up on trying to source the bad wire) its the wiring harness from the fuse box to the alternator. He believes (I have not seen proof yet) that the number 13 fuse wire is causing the short. Its like a 60 dollar part with a close to 600 dollar install cuz of all the wiring =) Good ol' GM. Also yes, I've noticed Bright Red cars have a lot of issues, but its ok, cuz the car looks.. damn good.

jfb

If you follow the output wire on the alternator, it goes back to the jump start bolt behind the battery and it has a bulge in it which is the fusible link. Connect an ohmeter from the positive battery terminal and the alternator output bolt, it should read the same as touching the ohmeter probes together. If not, then you have a blown fusible link which can be replaced. Your mechanic needs a refresher course on 88 Vettes! The alternator puts out 14.7 volts cold and this drops to 13.7 volts when the alternator gets to its normal operating temperature. Your dash voltmeter will read 0.3 volts low because it reads the voltage after the ignition switch contacts which have about 0.3 volts drop across them.
Lead acid batteries are considered discharged at 12.0 volts, so your 11.6 volts tells me you should get a battery charger and recharge your battery overnight. Alternators get very hot charging up a dead battery and this shortens their life!