cph81

I noticed my headlight, dashboard light, and the radio light are dim when the car is at idle. Is the alternator going bad?? or something else.

Greeny

iTrader: (43)

Check the voltage with a multimeter at the battery while it is idling,it should be in the high 13 volt to low 14 volt range....

goon9

iTrader: (13)

Try cleaning the battery connections. A bad alty will won't be paferful enough, causing you run off the battery. Then the battery goes dead.

I think when Mine went, the e-brake light and the battery light came on and wouldn't turn off.

Sounds to me a bad connection near the battery.

89blackse

iTrader: (2)

Agreed. My car would do the same thing, and when I would go to turn off my car, with the first click of the key to the off position the whole car would go dead, like the battery had just died. A subtle symptom but it turned out that the negative connector had rusted through and was just hanging on the terminal. Not easy to see unless you were looking right at the battery.

Good luck

colinnwn

To figure this out without chasing your tail, you really need to be methodical. I am not sure what the FSM says to do, but generally the following is a good procedure.

1-Remove positive terminal from battery and test voltage at battery. It should be 13-14 volts. If it's not, you have a weak alternator or dying battery. If you have a battery charger, try charging it per the instructions and retest. If the charger doesn't improve the battery, its a dying battery.

2-Remove, inspect, clean, and reinstall battery and car terminals. The terminals must be tight enough they don't move when twisted firmly with hand strength. Retest voltage at battery. It should be the same as the battery was disconnected. If it's lower, you have dying alternator diodes, or some other problem in the car wiring harness.

3-Start car and test voltage at idle with all accessories off, it should be a little higher than battery voltage. Test voltage at 2000 RPM, it should be pretty much the same as idle. If either of these is lower, it suggests a bad voltage regulator or short in the alternator windings.

Juicey

Alternator won't be a problem when you're driving. I had to replace mine recently. It drained an brand new battery even though Advanced Auto Parts told me the alternator was fine (after some test they do).

If you have to replace the alternator check your belts since they are in the same area (one belt is on the alternator itself). I had a shop replace all three belts and the alt. because I was lazy.

Cost's around $147.00 for a new (re-manufactured) alterntor. The belts range in price from $18 - $30 I think.

I was charged $210 for labor.

cph81

Thanks for the info.

I cleaned the termainal. I jumped start the car and check the charging voltage. It was ~top 12V to low 13. I drove around ~10 miles. The dimming light starting happen again. I drove back and check the charging. It was ~8 to 9V at idle. I rev up the eng and just jump up to ~12. So it looks like I need to replace my alternator. Anything I show check before I go to change the alt.

Scope

iTrader: (5)

Is the battery light on?? The battery maintains the entire system at 12.5v. Anything after that is the alternator. My guess is that the battery is dead and you are running on you alternator. What's the battery's voltage with the car off. If you have a spare battery check it out first before replacing the alternator. To me it sounds like the alternator is doing all the work and the battery isn't.

internetautomar

iTrader: (30)

Toss the battery on a charger for a couple of hours, and see if that helps.
My infiniti had a bad battery so it would run (kinda) off the alternator.
swapped out the battery and things went back to normal.

cph81

Bad battery effect the charging voltage??

The battery light never came on. The only time it came on is when I turn the key to power up the car. It will go away after start.

I'll try another battery.

Thank you for all the replies.

colinnwn

A battery with a shorted cell can cause the alternator to not be able to raise the voltage to its normal level.

The battery light just means the system voltage is low, it could be caused by anything.

Actually since you said the battery was about 12v after a jump and 9v after a drive, I think its a bad alternator. But that is not certain.

Jon94SE

Alot of times dim lights can be just bad connections/grounds save your self some money and check the simple things first.

Scope

iTrader: (5)

Regardless of bad alternator the battery is supposed to maintain a 12v charge. When my camry alt went I was only reading 12.85v at 2000 rpm and 12.4v at idle.

I think your alternator is trying to run the electricals after startup. That is why I am guessing the battery is dead. It may have enough juice to start the car but after that the alternator is doing all of the work. Check and clean all of your grounds, check your battery and see if you have the proper water levels, recharge the battery and clean the terminals, if all else don't work then replace alternator and belts.

cph81

I put a new battery on it today. After I warm up, idle @800rpm charging was @ 12.42V. Rev up to ~2000, charge at ~13.4. I drove around for 5 min and check the #. They r still the same. Does the number looks OK?? Is it a weak alt?

Greeny

iTrader: (43)

Them #'s don't sound too good to me..I think your alty is slowly going out..

Scope

iTrader: (5)

Check them after a few days. But plan on replacing the alt within a month or two as it was being stressed from charging a dead battery.

kmiller

Don't they say that the alternator starts making a funny noise when it's almost on it way out?

internetautomar

iTrader: (30)

those #'s are a clear indication of a bad voltage regulator which is internal on our alternators.

But make sure that "new" battery has a full 12+ volt charge on it.

GRNMAXDMON

iTrader: (1)

im havin' the same problem now. i went to start my car today in the mornin' and the when i just turn on my parkin' lights my rpm's drop (this is when its in a cold start) then when i shut off my rpm's go back up. i also noticed that my dash lights came on pretty dim but in a fadin' way not like when u turn them on they just come on. my battery is only about 4-5 months old which is an Optima Red Top and the alty got replaced like 6 months ago. but as i was thinkin' later in the day i realized that i don't have my splash gaurd where my alty is at and just last week i drove my car in the rain but can't recall if i went over any puddle. maybe that might have shorted my alty but i will check anyway just to make sure that i don't drain my Optima Battery.

colinnwn

@kmiller
A noisy alternator means its dying, certainly when a bushing is toasted. But a dying alternator does not always noises make, eg. when the regulator is bad.

@Scope
An alternator will not die from having to fully recharge a dead battery, unless the alternator was already on the way out. Now if it had to recharge a dead battery every day for many months, it would reduce the expected service life of an alternator.

@GRNMAXDMON
The appropriate way to diagnose your problem is to look in the FSM or refer to #5. I would highly doubt an Optima would die that quickly. I would suspect a poorly rebuilt alternator would die that quick. Alternators are designed to get road spray in them to a limited extent. It would be suprising if lack of a splashguard was your primary problem.

For your situation, since the battery can start the car (which requires by FAR the most juice) and the car runs fine (which requires little juice), it suggests a bad voltage regulator. The regulator can't appropriately maintain voltage during the increased demand for power from the accessories.

GRNMAXDMON

iTrader: (1)

well, the thing is that i never buy a brand new alternator. i usually get both of my alty's rebuilt. one for the car and the other i have as a spare just in case the 1st one goes but i will run some tests and c what is causin' my problem. but i figured since i didn't have the splash gaurd, water would go into the alternator and just short it out.

colinnwn

I wasn't trying to sound down on rebuilds (unless they are from AutoZone). I usually use rebuilds also. If you got them rebuilt from a reliable shop, it could have been a fluke bad one. Its suprising to hear you feel like you need to have a spare onhand. In my experience, Nissan alternators last 5-7 years. Not frequent enough for me to feel like a spare is necessary, but maybe we have different thresholds of reliability. It will be interesting to hear what your problem ends up being.

GRNMAXDMON

iTrader: (1)

i always keep spare parts for my car. i practically have about 50% of spare parts layin' around for my car. even a spare 5spd tranny just in case mine starts to give problems that way i don't have to spend another 2 1/2 yrs. lookin' for another one just like my 1st one. i had a spare engine but just gave it away cuz it had a broken crankshaft snout which came out of my old '89 SE. when i have time i will try and figure out what is wrong with my car.

datsun40146

Try cleaning you contacts, having them with corrosion will sned low volts ect, and cause what you are looking at.

jorgeg73

i am having a worst problem i what to turn on my car and all the leds are on but when i turn the key to turn on the car it dies, i also noticed that when i trun on the lights the dashbord dies to than slowly it goes back on like nothing happens

colinnwn

Your starter is probably toasted. But before you take the starter out, I would test the battery to be sure it is over 13 volts. If not, recharge the battery to at least 13.5 volts and try to start again.

PovCityHustla

Just before my alternator went out, first the amp for subs would cut out, then the headunit would cut out. I think when the computers knows the battery charge is low, it cuts out all un-necessay stuff eg amp, headunit etc. Hope this helps..

internetautomar

iTrader: (30)

actually it's the units themselves trying to save themselves from low voltage

alextothestars

my abs light came on when the alternator went. started "dimming" and running sluggish. then it wouldnt start. charged...wouldnt hold a charge. clicked and abs light stayed on. alternator. fixed the next morning.

Scope

iTrader: (5)

The job of an alternator is to maintain the system. IF it has to recharge the battery and maintain the car's electrical load day by day then it is being overstressed and that will kill an alternator. That is why I have been questioning the strength of the battery as it may be over stressing to charge a dead cause only causing more stress on itself.

hamimp

Since I see lots of helpful posting related to my alternator/battery (probably) issue and I cannot post a new thread yet, may I ask these (if is not right to post here, I will take this message out):

1. At idle (engine running with no load), I get 14.2 Volts.

2. While I run with load and press accelerator), battery maintains 14.2 Volts.

3. When I go downhill (with no accelerator pressing) or drive slow (around 20 mph in the neighborhood), I see the voltage drops very quickly to 11.8 volts. And keeps there. Sometimes it drops from 14.2 to 11.8 in just 2 seconds and maintains that (I am using car chip and hence can tell these data). But, then as I speed up, voltage gets back to around 14.2 Volts.

4. Now, I had twice car stopped while driving in low speed. And in one case, it started waiting a while and in another case, I needed a jump start. In the last 2 weeks there is no issue.

5. Also, I hear a hissing sound near the alternator when in idle.

Now, one dealer said, everything is OK, while another said replace the alternator.

I took it to Napa/Autozone - all said, electrical charging system is fiine.

Please tell me what do you think - it is battery, alternator or some other shorting issue.

Thanks.

internetautomar

iTrader: (30)

how could you use carchip?
I thought that was OBDII only

Tquick

Obviously, this is something intermittent. It is possible that it is the alternator. General maintenance of the charging system includes verifying that the alternator belt is in good condition, and properly tensioned, and cleaning and tightening of all connections in the main charging circuit (battery terminals / posts, alternator, starter, and ground at block). If none of that fixes it, then I'd say change the alternator.

Maxima9750

That could be a bad alternator since I just replaced mine about 3 months ago. It did those exact same things for awhile (lights and gauges got dim). Eventually, my ABS and BRAKE lights came on every now and then, but when I put the brakes to the floor, ABS kicked in, immediately stopped the car, and both of the lights turned off. I had the alternator replaced and all problems went away (except for my torque converter blowing out about a week ago).

colinnwn

At the auto store did they remove the alternator and put it in a test bench before they declared everything OK? On car tests are not 100% reliable. It sounds like a dying voltage regulator (which is in the alternator) to me. A bench check will catch this.

Also, what is the voltage of the battery when it is disconnected from the car, and when it is connected but the car is not running?

internetautomar

iTrader: (30)

NO alternator test is 100%
The alternator on my first VE, was testing good on the car and off the car. Guess what, it was bad.

colinnwn

You have a point. But off car tests are considerably more reliable than on car tests.

While I don't have data to back it up, I would think the newer computerized test stands that spin the alternator up, do diode, voltage regulator, and output tests, are pretty close to perfectly reliable as long as the tester follows the directions.

In your case with the erroneous result, was it a modern computerized test stand or an oldie?

internetautomar

iTrader: (30)

don't recall anymore.
But I do know that the only thing a computerized off car tester tests besides voltage output is that the diode is good.
all the testing you want is not a replacement for real world driving.