Today i had my battery checked to see if it was good, because my car died last night. The whole time the battery light was flickering. So after getting it checked, it was still a good battery. So i put i all back in and check all the connections and i found that the nut holding the ground wire to my alternator was missing. So i put a new nut on there and plugged in the battery and it started fine, and was idling high at first but i guess the battery needed to be recharged. So after running it for a little while i drove it around my neighborhood and the battery light stayed on the whole time i was driving it. The voltmeter read between 11.4-12.1, no lower no higher. Is my alternator going bad because before the volts read at about 13.7-13.9. Can someone tell me what they think is going on? Thanks..

 

With a DMM measure the voltage output at the alt power lead, wrt ground.

If the output is still below 12Vdc at the alt, replace it.

 

The Altenator is nortorius for going bad in the L98 cars due to the high heat. You can drive the car to most auto parts stores and they run the check for you without problems. Due to the heavy electrical demands of the car low power (whether battery or altenator) will sometimes give off wierd signals

OR you can do the junk yard thing and unplug your battery while it is running to see if the altenator can maintain voltage at idle (this is most difficult part for the alternator )...but because it may fry your ECM from EMP it is lot safer just to take it to a auto parts dud and let their machine test the whole system for you.

 

:seeya
I had a similar problem before.

You are correct, when the engine is running your voltage should be near 14 volts. 11.4volts-12.1volts is WAY too low. If everything is connected again do this. You will need a multimeter set on the voltage scale. They cost less that $20 at an electronics or local hardware store if you do not already have one.

Here's how to find the problem. It only takes a few minutes with a multimeter.

1. With the engine off, multimeter set on the volts scale, connect one lead to the positive battery terminal and the other to ground somewhere. (The nut that secures the cruise control cable just above the pos battery terminal is a good ground.)

2. The voltage should be close to 12 volts or higher. If not, your battery is too low and should be charged.

3. Start the car. Do the same thing as above. You SHOULD see your battery voltage jump to over 13volts and close to 14volts. Note the voltage you just got here. If the voltage does not change when the engine is fired up, your alternator may not be charging. Recheck your wiring too.

4. With the engine idling connect one lead to the thick wire that is attached to the alternator by a nut, and the other lead to ground. ( the small upper alternator bracket nut is a good ground) This voltage should also be above 13 volts and should not drop. It should also be the SAME as what you got at the battery. If they are NOT the same your alternator may not be charging.

5. Note the two readings you got at the alternator and battery(if they are different you have a problem) and now look inside the car at the dash voltmeter. It should only display about .3volts lower that what you got with the multimeter.

If it shows 11.4-12.1 as you described, AND you get over 13volts at the alternator and battery when idiling, your dash guage is incorrect.

If your two readings at the alternator and battery are not the SAME, you have a problem with the alternator not charging.

I solved this by rebuiding my own alternator. I replaced the brush assembly, the rectifier assembly, and the voltage regulator. That solved my problems for and for less than $60.:D :D

Hope this helps you man. :thumbs: :auto:


[Modified by 86PACER, 5:35 PM 1/5/2004]

 

Most likely it could be your voltage regulator needs replacement. Depending on the mileage you could also replace the front and rear bearings. I put a 100K on my 85's alternator before I replaced these parts. There is a method of checking your voltage regulator on the car with the engine running with just a screw driver inserted into the rear of the altenator. If the voltage increases with this test, it indicates that the voltage regulator is bad. This test is in service manuals.
If you try this replacement yourself you will most likely have to take the alternator somewhere that has an impact wrench to remove the front nut on the shaft. New bearings and a new voltage regulator installed by a alternator/strarter shop in the Houston area should not cost a fortune. If you are going to replace it, Advance Auto sells AC Delco factory rebuilt alternators that shold give excellent service.


[Modified by 70ZZ3 96LT4, 3:32 AM 1/5/2004]

 

The voltage measured at the battery terminals and the alternator output bolt must be the same or the fusible link in the wire on the alternator output is blown and the alternator cannot charge the battery. If with the engine running you measure 14+ volts on the alternator output and 12v on the battery terminals, then the alternator is working but the fusible link in the alternator wire is blown and should be replaced.

 

Nice job.... :thumbs:

 

I think I have the same problem. I also note my dash lights seem to flicker. I first thought the radio (Bose) was bad because the light flickered. Car would be dead after sitting a couple of days. I replaced the battery. Didn't help. I get ALMOST 14 volts then sometimes 11.6... We were going slow looking at Christmas lights and when the fans came on it dropped down so low the anti-lock brake warning came on and the lights went almost out. Believe it or not it didn't die and I punched it and drove home. Even then I got 13.6 then 12... then 11.6...11.4... I just ordered a supposedly NEW alternator from a company for $102 Shipped! I'll tell you how it looks/works/lasts...

 

onrecess,

:seeya
That fluctuation in voltage DEFINATLY sounds like the alternator, or a loose connection somewhere. I had to deal with that SAME problem twice in the past, beleive it or not. :nonod: Here is what it was on my 86.

I was on a long trip to Los Angeles and about 2 1/2 hours into the trip on the freeway, my voltage suddently dropped to about 11.8volts, fluctuating very odd ! :eek: I BARELY made it to a local Autozone parts store before she died. They loaned me some tools and I removed my alternator in the parking lot in about 5 minutes. One of the 3 electrical terminals that are soldered on the inside came off. I purchased a $9 soldering iron and a roll of solder, and re-soldered it all right there in the store myself. That INSTANTLY solved the problem, voltage jumped to 14.1volts and I made it back home the whole 3 1/2 hour trip without a problem. :D :D

A few days later AGAIN the same as you described. :crazy: WTF? This time it was the thick wire that is held by a nut to the alternator. The post was loose. I had to open the alternator and tighten the nut on the inside that holds that post for the teminal. Problem solved. It has been almost 2 months and all is well now. :D

Good luck with yours onrecess :thumbs: :auto:





[Modified by 86PACER, 1:33 PM 1/6/2004]

 

FYI: just replaced the battery cable nut that attach the cable to the battery, the threads were sightly stripped and really not attaching tightly...

 

I've found that the digidash voltage guage is exactly .5 volts lower than the actual reading at the battery. (Dash showed 12.5, and I had 13 volts at the battery)