Hi all,

Problem just started this morning.

When I turn on indicators, lights, use windows, etc... lights on dash dim (each time indicator blinks, or I hit brake pedal and lights go on, etc...) voltage drops from 14.5 or so down to 10. If I turn lights off, turn off indicator, etc... voltage climbs back up to 14.5 and stays there until I use an accessory again.

The car is still running fine while this is happening - no engine stutter or anything.

Is this a problem with the battery holding a charge or with the alternator?

Thanks for any help!

Jason


[Modified by jasonberkeley, 8:28 PM 4/1/2003]

 

I'd like to know too. I have a similar problem with my C4.

 

It really sounds like the alternator or related charging system defect. It is not the battery if the car is running and those symptoms are present. Check it with a multitester to see how much voltage is going to the battery.

 

I'd try to go step by step until a more noticable effect is known, for example if turning on the running lights doesn't do it, but turning the headlights on does. I'd then proceed to examine everything related to the headlights. Good luck :cheers:

 

My car did this exact thing. It was the battery. It did it with the stock AC Delco when it started leaking. It did it again with the piece of crap Diehard after about a year.

My OPTIMA REDTOP solved the problem permanently.

:flag

 

My best "guess" since that is all we can do with out testing either alternator or battery is that they are both bad due to the altnerator going out and now the battery cells are damaged and not holding a charge. Autozone or similiar should be able to test them for you while on the car.

 

I am having the same type of problem. Sometimes the voltage drops to 13.2 and sometimes goes as high as 15.1. When I use the head lights and press the brake the lights dim some, also the votalge will drop by about .3 volts or more. I am taking it in friday to have them check it out. I think it is prob the alt or reg (on chev they are all in one unit). I don't think the batt is bad. The car starts just fine. I have had the DIC say "Charge Fault" when I have first started in the morn. I clear it and never see it again that day. Today I started it and my voltage showed 11v :eek: but slowly moved up to 14.2 volts.
:sad:

 

Hi all,

Car is driven everyday, so it wasn't an issue with it sitting for a long time.

Shop checked and said battery was ok, and alternator was bad.

They swapped the alternator out, left the battery alone, and so far so good!

I'll keep you guys posted!

Thanks for the feedback!

Jason

 

I should know in a little while what had to be done to mine. I think it will be the same fix as yours. :)

I just got a call and they said they could not find a problem. He did see the lights dim, but said the tech said the voltages were within spec. :mad
I told him that it never did this the entire time I have owned the car (more than a year) until about 3 weeks ago. He is going to talk to the service Manager to see what they can do.
Were did you bring your car. Can you give me the service advisors phone number so that I can have them talk to him or her. If it fixed your problem it should fix mine.

Thanks for the help.

chuck



[Modified by TXSTICK, 11:37 AM 4/4/2003]

 

Don't look at the voltage reading on the DIC until your car has been running for several seconds.
On C5 the alternator does not begin charging for what seems like an eternity after the car is started.
This is normal. Voltage should be between 11.5 and 12.6 volts on startup.
(with variations)
After a few seconds it should go up into the 14 V range.
Please note, GM alternators have temperature sensing circuitry that will change maximum output voltage lower or higher to compensate for high or very low ambient temps to protect the battery from damage.
Dimming lights at idle are normal on all GM cars and light trucks.
The lower rpm of the engine reduces the current producing power of the system, the heavy electrical loads tax the charging system and the voltage will actually drop. I am sure a lot of you have noticed things like the fuel pump changing pitch when you have your turn signals on or when you hit the brake, dim lights, and changing instrument backlighting are all normal occurances at idle when electrical loads change.

The explanation is not complex but it does take some time, if any of you have access to TSB information look up GM bulletin 02-06-03-008, this explains the normal conditions which you will all notice.

Once you begin to accelerate and get the engine rpm's up the gage should return to normal. I have replaced many a battery in C5 but only 1 or 2 alternators so far.

This whole thing is one of the reasons car manufacturers are getting ready to go to 42 volt electrical systems. More voltage means less current will be needed and electrical systems should be more stable.
The problem with using 12 volts is that you need enormous amounts of current to control todays electrical loads and the generator just can't keep up at low rpms.

Hope this information is helpful.

EWill

 

Normally, If the car is running and you are having power problems then it's the alternator. If the car isn't running, then it's the battery. Of course, there could always be a bad connection somewhere. An easy way to tell if you are at idle is to give the car a little gas. If the lights get brighter, then you most likely have a charging/alternator problem. :cheers:

 

$.02 info
Sounds like battery not having enough capacity to run the car, and or could be shorting internally. I would replace the bat. The alt is producing voltage at 14+ but you don't know the amps. I am guessing you are pulling high amps from the alt due to the batteries inability to surge the load.

Diehards Batteries .. :lolg: :lolg: :lolg:

 

Good comment! I had the SAME problem and it was finally fixed after they
changed the alternator and when the AGM battery finally crapped out.

I really noticed the probem at night when I sould apply the brake in traffice.
I could see the headlights dim in the refection from the car in front. The other
big current hog is the windows.

GM will not replace a battery until the voltage drops below 11 volts. My old
(semi-sick) battery was at 11.2 to 11.5 volts. The guage on the DIC and the
analog meter are useless in reading battery voltage. Try it at the battery with
a volt meter.

Good luck...it took me a year to get the problem fixed.

 

well, they checked the alt and batt and said it was all putting out what it should be. I talked to the service manger and he called GM. He called me back and said they did not know of any problems. :mad I told him that I have driven this car for 15,000 miles and this just started, and that it is not normal. I have only had the lights dim when using the power windows while driving and I expect that to happen. But not when I am going 45 and put the blinker on, or apply the brake. Since I had it to the shop, now the voltage has stayed between 14.1 and 14.3, except the lights dim for a second sometimes when I hit a bump in the road. This tells me that there must be a loose conection somewhere. By the way, my lights do not dim now with the blinker or brakes. They must have been pulling on the cables when testing and have made the problem better. Also I did notice that the AM side (testing only :) ) of the radio was very noisy before I took it in, now very very little noise.) Loose connection? I think so, before I was thinking alternator.

:sad:

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[Modified by TXSTICK, 6:41 PM 4/10/2003]