Hey guys, wondering if you fine gents can help me out with this issue im having. My battery light has started to turn on and off randomly while driving. Accelerating hard turns it on, and accelerating very slow seems to not trigger it often. When the light comes on the lights on my cluster and headlights dim and my acceleration seems slightly slowed. Idle doesnt seem to be affected.

Things ive checked/noticed:
-Battery checked, rated at 700 and tested around 650.
-Positive cable loose/grimey, cleaned recently but still loose.
-Alternator Belt loose possibly? A belt squeels from a cold start.
-Radio is very static-ey while the light is on.
-Idling for around 1 minute will turn the light off.

Thanks for any help in advance guys. PS it is a coupe if that matters.

 

Replace your lose positive terminal. Check and clean all of your grounds. Tighten the alternator belt, and have the alternator tested.

Your either getting really bad ground, belt is slipping REALLY bad, or your alternator is heading out.


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Ok so i tightened the belt and the positive terminal. Im going to pull the alternator out and get it tested when i have the time for it. I did have the auto store test the battery with the car running after i had been driving it for about 4 hours, it checked on 11.2v while the engine was on if that could give any ideas. Where might the grounds be, if you dont mind me asking? I am fairly certain that most the components in the vehicle are completely stock, so it wouldnt surprise me if its failing after 20 years lol

 

Sounds like the belt is loose.

However your battery should have a higher voltage reading. You could have two issues. I would replace the battery and with the alternator belt tightened see if you can get it to replicate the issue.

To check belt tension, on the longest side of the alternator belt, and in the middle of that side, try to twist it with your fingers. It should only twist about 90 degrees. If it twists more than that it needs to be tightened.

If it still does it after tightening the belt and after replacing the battery you need another alternator. I would recommend buying only Denso alternators.

Your ground is underneath the thermostat housing. You will see a bronze type of wire attached to the housing with a bolt. Take it off and make sure it's clean and put it back on.

 

Awesome thanks for the info. So i think i might have confirmed its the alternator, tonight while i was driving to work the lights got very dim in the cabin and the headlights, it progressively worsened as the tachometer and speedometer wouldnt work properly if i had the headlights/daylights engaged. Sure enough i parked the car and turned it off, when to turn it on it wouldnt turn on in the same manner that a dead battery behaves. Managed to get a jump but the same issues occured, if i had the headlights on the car would stutter.

 

Sorry for the double post but i have some updates.
-Pulled out the alternator, it tested good. voltage was 13.4 low 15.4 high 14.4 average or around there.
-Battery tested super empty, had it tested at walmart and they charged it instead of replacing. After driving it for 5 mins or so, the light is back on.
-I cleaned out the aforementioned ground.
I will hopefully be able to get them to replace my battery, if not anyone else have any ideas?

 

How did you test the alternator with it out of the car ? Did you take it to an auto parts store ? You can test it in the car. It should not be getting a voltage reading of 15.4. Something is not right there. With the alternator in the car, load up every accessory one at a time and check the voltage. It should always read above 13.00 volts minimum even with everything electrical in the car on. The light is not a battery light, it's a charging system light. It will come on if the alternator voltage is putting out less than the battery is currently at. Normally this light won't come on if the battery is bad, usually if the alternator isn't able to put out enough voltage to power the car. However, I suppose the battery could just be bad. It's not impossible.

 

Oh sorry i should have specified yeah they did their load test with their machine at the auto parts store, im not sure if it was running 15.4v he just said that was its max output. I managed to get a new battery though after the charged one was coming up bad. Also thanks for the info about the light i didnt know that, probably would explain why the light was on as i put in the new battery. I'm assuming i attach the voltmeter to the alternator directly or the battery? Im going to try this since i think it is the alternator and the machine is lying honestly.

 

Sorry for the double post but i took the car to get the alternator tested at another store, turns out they know how to do it lol. turns out my voltage regulator failed(go figure). Anyone know how far i can run a battery without it?

 

It's not good to run a car with output higher than 15. It can cause the battery to boil over and possibly explode from what I heard. Since your alternator is bad, I would suggest replace with a Denso only. You can get the best deal normally at rockauto

 

Yea i went ahead and took your advice, replaced the alt and everythings running fine now. Although i did get the crappy O'reily Ultima Alternator, if it craps out on me soon im going to just return it for my money and get a Denso though. Thanks for the help man, much appreciated.

 

hi there, i was wondering if i can get help on the same topic.. keep in mind battery and alternator is brand new, i just want to know what causes my battery light to come on.. start engine---- wait for a few minutes--- then bam light comes on, but funny thing is that the light turns off when i rev my engine and light comes on when idle is at ease... any clues on whats goin on here??

 

First check that your belt isn't slipping...normally you can hear it squealing most when you first start the car from a cold start.

Assuming the belt isn't slipping, on average most auto parts store alternators tend to average the first one bought to be bad and getting a good one on the second try. lol

If you bought a Denso however you have nothing to worry about with the alternator reman. But if it's not, it could just be bad.

 

Can't remember, all the different gen's....but isn't there a rubber "ring" on the crank pulley? If so, draw a line on the pulley. From the inside to the outer edge. Run the car for a bit and re-check the "line".

 

@holmesnmanny: actually, yeah my belt was squelling first and then ppl at o'reilly told me to put some baby powder on the pulleys? and whattaya know it stop squealling.. but a mechanic told me online (keep in mind battery and alternator is brand new) it might be a failing main relay (which was recently changed) and/ or fuel pump/ fuel filter going bad?? any other suggestions?

 

Did you draw a line on the crank pulley and then re-check after driving the car?????

I'm not as stupid as you think and the cost to you.....nothing but time so why not humor the stupid person.

Here is the thought.....if the crank pulley is slipping on the "ring" than at idle the alt is not being "spun" enough for it to give a proper charge, hence the light is on.....you give it gas and then there is enough "rpm's" on the alt to get the proper change and the light goes off. The parts store tests the alt at the proper "rpm" so yes it checks out.

I've been around long enough to know that I can and will be wrong but at the same time I have seen all kinds of thing before.......so again get a tire crayon or sharpie (if you don't own one it is all of ~$3 for one), draw the line, run the car and prove me wrong.

If you do, I've still got a couplee of other ideas.....one of the first ones....when this happens what is the voltage at the battery terminals as the car is running vs the voltage from the "charge post" of the alt?

 

The only reason you ever put something on the belt is to verify that the belt is too loose. Then you simply need to tighten it up and check and see if the charging light doesn't come on anymore.

Do what Lost_again said. It makes sense.

You can also try to twist the middle of the longest side of the alternator belt with your fingers. It should only twist 90 degrees, no more. If it does, the belt is too loose.

The main relay has nothing to do with the charging system.

 

thank you guys for the reply i will definately try this...
and @Lost Again: im still unclear of what you ment by drawing a line, can u send a pic or a step by step process? thanks....

 

On the crank pulley, use a crayon/sharpie to make a line on the face of it. You should see a small seem/gap from the inside to the outer edge of it.

Just make a line/mark from that inside part to the "outer edge".

Run the car. If that "line" is not a line anymore then the rubber ring on the crank pulley is slipping/gone. Meaning the inside of the pulley is turning but the outside (that dives the belt(s) ) is not spinning at the proper rate

 

here's a link of the same problem on my car..

 

More important than the light is what's going on with the voltage as the light comes on and off. Have the battery tested and if it passes have it fully charged then install it and check the voltage while the car is running. It would be best to check it while the car is completely cold started. At that time it should be putting out 14.60 with no accessories whatsoever on. If not then the problem is probably the alt.

 

Can any one telling me what if Battery light doesn't go on while Ignition Switch is turned on, and ALT fails to charge the Battery?
Battery is brand new, I just seviced the ALT ( Bearing Changed ) Fuse on both under Hood & Dash are intact and OK,
Once few days ago it came on and Battery got charged , but again head lights dimmed and battery weakend.
Is there any hidden cause for such defect? the overal check showing all connections & body strap are in place and fixed. could it be caused by the defected Voltage regulator ? What do you think.
Best regards and
Much appreciated and welcome technical due comments.