[FLABOY777]

I have a 96 caprice with 4.3 and battery(yellow top) is good and alternator(140amp) is good got it checked at a shop,but when its in drive and the ac and headlights are on the voltage will dramatically drop,i have to turn the ac and lights of in order for the voltage to go up??checked couple things but have no idea!! radiator support was changed since it was in a accident and pass-key fault light stays on but doesnt affect car so i just took the bulb out???anybody have any idea what it could be,also the short ground that goes to the fender next to battery is loose but that shouldnt cause it to do that?????

 

[FLABOY777]

also i;ve pulled all fuses out one by one when it happens but that doesnt seem to help?also disconnected trunk light incase it was sticking!!!

 

[Gregg-O]

If it drop's a little at idle, in drive, with A/C & lights and stuff on I wouldn't worry ...as long as it comes up when the rpm's come up. Tighten the losse ground fool !.

 

[BandGbodies]

What he said. I've seen with mine that in the morning when I'm leaving work, with the defrost on, blower on high, rear defroster on, and the hehadlights on that the gauge is reading about 3/8ths of full scale at idle. When I hit the gas, the voltage comes right up.

 

[KaeJR]

Are you running any type of sound setup (subs and amp)? if you are then that would have something to do with your voltage dropping at idle as well. There shouldn't be a SEVERE drop of voltage with just having the headlights and AC running. I would check grounds as well as the overall integrity/condition of the power wire running from alt to battery. I was having major voltage drops over the past 2 weeks I have 2 red top batterys and just thought that one of them had gone bad, come to find out that the power wire from the alt to the battery had burned and it wasn't sending enough current through to keep the battery charged.

Have you tried using a volt meter to check the volts at idle and while being revved? that is also something you may want to do

 

[FLABOY777]

so then its fine if my voltage drops damn near to half of the gauge then it goes up when i accelerate???i never had this issue with any other caprice?also im not running any sound system!took it to the shop and they said it was charging fine,but it just dont seem right to me for the voltage just to drop and start making the lights dim???the car sat for a couple of years could it need some new power cables and grounds???garys cables,big 3???????thanks everyone for the input.

 

[KaeJR]

Once again an easy way to eliminate the what ifs is to go to your favorite hardware store or WalMart and purchase a volt meter, check your actual outputs with a digital readout and see how low it is actually dropping.... The Big 3 is a great upgrade but is not important if you arent running any power hungry accessories (subs, amp, hid's etc.) if you find that your battery cables are in need of replacement that would be a good time to do the Big 3 upgrade..
I do have a question, does thr dimming and voltage drops happen as soon as you get in the car or is it fine for a while and then happen? Checking grounds and tightness of connections are always one of the first things you should do during troubleshooting


FYI : if you dont have any major accessories hogging power then your readout on the volt meter shouldnt go below about 13.2 at idle (give or take a few .1's) hope this helps

 

[FLABOY777]

Kaejr It Happens A Little After I Start Driving It Will Just Drop And I'll Have To Shut The Ac Off If Not When I Stop At A Red Light The Voltage Will Stay Low Until I Accelerate! I;ve Checked All My Grounds And They Seem Ok Except For The One That Goes From The Battery Ground To The Fender Could That Really Have That Effect On The Car?and The Ground From The Battery To The Block Looks Good But Looks Like There Might Be Dirt And Grime Around It?

 

[KaeJR]

Yeah believe it or not grounds do have a lot to do with it but without knowing exactly what the volt readings are you're going to be looking at things that may not be the problem. Please get a volt meter and get the readings, you never know, it could be completely fine but you are about to embark on a journey of unnecessary spending if you don't get right to the problem. Clean that spot that you said has a lot of dirt and grime and make sure that the terminating point is making a good connection with the metal.