For the past couple of weeks, the voltage in my car has been at either 12-14 volts, or down around 8-9. Tonight when i was driving home, it got way down below 8v, into to the red lines on the gauge, and my stereo cut out, and my headlights got really dim, then after about 10 minutes of this, it suddenly jumped back up to 12v and everything was fine. Is my alternator going out? Any other ideas on what this could be?


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1992 Camaro RS L03

 

Sounds like a bad ground or connection to me, clean all your connections good, if it's making a whining noise and gets real hot as soon as you start it up it has bad diodes and needs to be rebuilt.

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92 Camaro RS 5.0 5-Speed (Quasar Blue)
T-Tops
14" Open Air Cleaner
3.08 Posi-trac
Edelbrock TBI Intake
Crane cam
Ported & polished stock heads 3 angle valve job
HyperTech Chip
SLP Headers (Ceramic Coated)
UltraFlo cat-back exhaust

74 Dodge Dart Sport 360 (11.2 1/4 mile)

2000 Dodge 1500 Ram Sport

 

Check to make sure your alternator is charging properly. With the engine off, get a voltmeter and check voltage across the battery...should be about 12v. Then start the car and check it again...should be around 14v give or take and the voltage should also be seen on the dash guage (assuming your guage shows numbers). If you see an increase, then your alt is doing its job.

Make sure you turn off all your accessories when you do this so that your charging problem is not being caused by some type of electrical short.

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92 Camaro RS, LO3, 5-spd, T-tops

Performance:
K&N Open Air Filter, Edelbrock performer TBI intake, Fastchip Prom, Timing +4 degrees, Centerforce clutch, Xact 8mm wires, SLP 1 3/4" Headers (coated), Flowmaster Catback Exhaust, Z28 Grille w/aftmkt fog lamps, MacEwen white-face guages
Electronics:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers.
NEXT UP: TBI mods, 3.42 gears w/Torsen posi

 

You probably have a loose or dirty connection to one of the wires connected to the alternator. Check all the wires to the alternator (at both ends).

Since the voltage swings so much so quickly, I'll also suspect that the battery is at best, discharged (needing charging), or worst, unable to receive a charge (needing replacement).

With a good battery, just disconnecting the alternator from a running engine should only drop the voltage from ~13-15 volts to battery voltage, ~11-12.4V, depending upon the state of charge of the battery and the load.

With a fully charged battery in good condition and the engine running, disconnecting the alternator should then give you 11.8 - 12.4 volts, depending upon the amount of load, and then gradually decrease from there. Perhaps a volt every hour or two or ?, depending upon how much current the battery is supplying.