I have an 87 L98 with a ongoing problem. I first had trouble starting it. Found out it had a bad starter. Replaced that and then the voltage started dropping as i drove. Had the alternator checked and it was bad Started it up and it set good at 13.9 volts and then when i started driving the voltage steadily dropped until i got home where it was at 9 volts. Turned off the car and turned the key on to watch the volts and it went back up to 10.5 but wouldnt start. The whole time the battery light was on. I had the battery checked and i was told it had a bad cell. Replaced the battery tonight. I started her up and everything was good no light 13.9 volts. Backed her up to take her out for a test drive and as i pulled out of the driveway the battery light came on and the voltage started dropping slowly. When i rev it the volts go up a little bit but not back to 13.9. What would cause this? Do i have a short somewhere? What causes the battery light to come on?? Any help would be great at this point. I am almost out of hair to pull out

 

The battery light comes on when the alternator is not charging the battery. Sounds like you still have a bad alternator, have it checked. Measure the resistance from the positive post on the battery to the large red wire on the alternator, it should measure the same as when you touch the ohmeter leads together. If it reads anything higher than this I would suspect the fusible link that is in the large red wire from the alternator. The link can be gotten to by removing the battery. It is one of the red wires that go to the jump start terminal behind the battery. Also, if your battery becomes discharged, charge it up with a battery charger overnight. Your alternator was not meant to charge up your battery and a dead battery draws a lot of current at first and this heats the alternator and shortens its life.
Also check the tightness and condition of the large red wire on the alternator, this is the output terminal. Be careful not touch a wrench to ground while tightening this nut because that wire goes to the positive terminal of the battery and touching ground will blow out the fusible link and cause a large spark!
Normal voltage readings on a good alternator is 14.3 volts (dash voltmeter) when you first start up a cold engine and the alternator voltage will drop to 13.3 volts when the alternator gets to its operating temperature.

 

Where do i get a fusible link for the 10 gauge cable running from the alternator to the hpot post behind the battery? Local uto stores only have the small 16/18 gauge ones.

 

Where do i get a fusible link for the 10 gauge cable running from the alternator to the hpot post behind the battery? Local uto stores only have the small 16/18 gauge ones.

 

Anyone??

 

UPDATE- Checked the fusible links and all of the cables and all is well. Took the car to an ignition analyzer. Battery and starter checked out but the alternator was found to be bad. Go figure a new alternator bad straight from reman. New alt should be here in a few hours. The moment of truth....

 

Sadly, It's not that rare to get a bad reman. part. I have learned not to rule out a reman part (especially alternator) until It proves to be OK. You might want to try rebuilding the alternator yourself. It is not hard ,is cheaper , makes a great Sat. afternoon project. Most times it is just a bad rectifier that can be had from most parts stores for around $15. A mulitmeter is all you need for diagnostics. If you are interested there is great proceedure in tech tips or you can find "how to" instruction on line.
Best part is , then you know it is done right the first time.

 

dwestsr is so right...I went the reman route some years ago...4 alternators in 10 days!...after the last one left me broken down on the Interstate I got the parts store to pay for the upgrade to an OEM AC/Delco alternator if I paid for my motel bill...

Never had problem one after getting away from those reman's...

 

Well just got the new alternator in and...it works but it is a reman and is only putting out 13.4 volts.

Afraid i might have to see how this one works until the weekend get here. So how is the reliability of the NEW alt. Would getting one of those help over these reman units?

It has got so bad i can remove/ replace the alt in less than 10 min. And that includes walking into the parts house to trade them out.....This makes 5 since last Monday.....

 

13.4 is fine with a fully charged battery-good luck.