Ace

what causes voltage fluctuations.. i know its load but with a 105 amp alternator you'd think that flicking the signal lights wouldnt cause the voltage to flicker.. i freaking hate that.. also if i watch the scanner, dvm, and gauge i can see them all move about .1V at idle for no reason contantly also any sort of load i throw at it takes it way down.. a/c.. defroster.. and the lights and it pretty much doesnt charge.. they can be eating up that much to soak it down to 11.5 volts i got the alternator checked and then the battery and they both pass the store tests.. but could it still be bad.. like it kinda works.. also the guy said my battery wasnt fully charged? could it be the alternator even though it passed? its a newer delco unit as well

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Danno

It pretty normal Ace. Part of the problem is where the voltmeter taps in to feed it. Chances are you will find if you duplicate the problem and measure directly across the battery terminals it won't be as significant. Most likely it's happening at idle. Usually coming right off idle it comes back up, at least it should. Remember, unless you read right off the battery you will see voltage drop because of wiring harness resistance and thats what the guage sees also. Another thing to remember is that when they rate the alt in amp that is BEST case, usually full fielded with a carbon pile load. GM rates thier CS 144(140 amp) alt for only a max of 124 amps in vehicle use and that's probably a stretch. With the lights, A/C, and electric cooling fans running at low rpm the alt simply does not put out enough. Next time around you might consider a CS 144 alt, it may give you that little extra zip you want. And yes, always make sure the battery is fully charged. The alt is not a charger, it only maintains the battery at around 80% of capacity. I always trickle charge my battery at least once a month-they last much longer and the alt does too.

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Ace

thanks! some good advice there... the trickle charging thing is a good idea..

i checked the signal light thing when the car wasnt running and it still did the flicking thing so im at a loss there... guess ill have to live with it or start changing bulbs/relays

83_1/2 L69

Fluctuating voltage readings are very common on our cars now that they are getting old. Many things can cause the dash Volts gauge to go wacko:
1. Loose or corroded ground connections.
2. Loose or corroded power connections.
3. Dirty contacts inside the ignition switch.
4. Funky fuses/fuselinks.
Like Danno says, the voltage at the battery is the most important thing to worry about. The battery will go bad if it is being discharged often.
On my car, I have found that the cigrette lighter socket voltage is very close to the actuall battery voltage (it dose not go thru the ignition switch). I have a small digital volt meter that I plug into the lighter socket. I just ignore the inacurate dash gauge.
My car came stock with a 144 amp alt. Battery voltage never dropped below 13.5 volts with all lights/fans on at idle. The alt (armature) shorted out 2 years ago. I replaced it with a 105 amp alt. I'll collect some voltage data and post it later.

Tyler-88

my volt guage flickers with the signal lights as well.

if your volts are dropping to like 11 volts with your accesories on, id say your alt is shot. i noticed my gauge was saying 13 constantly, than down to 12, than 11 than i replaced the alternator and it went back up to 14ish. id replace your alt, and if it doesnt fix it (it should) just take it back and say you didnt need it

Kings IROC-Z

I'm having the same issue with my 86 IROC. I've been having an electrical problem and have now replaced both the Alternator and Battery. I've now noticed that the voltage will significantly drop(With cabin lights dimming and blinker slowing down) with the A/C running with the car idle at a stop light. I was wondering if there was a Idling switch somewhere for the engine's RPM to increase when the A/C system is being ran at Idle? If the A/C is not on all other loads have a minimal effect on the instrument cluster Voltmeter. I'm pretty sure my Alt and Battery are now good but I could always double check