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battery light

3K views 19 replies 9 participants last post by  steveplatt28 
#1 ·
so the other night I noticed my battery light came on. but after awhile it went off. last night it came on again while driving, but then went off and would repeat this a bit. i noticed it only comes on after going 40mph or above for awhile, and then after slowing down or being stopped for awhile it goes back off. pulling from a light i thought i smelt something like a wire burning, but when i looked under the hood i seen nothing. everything looked fine. can anyone give some insight to this?
 
#2 ·
Hmmmm... Have both your bettery and alternator tested at O'reily's or whatever the equivelent parts store you guys have. Most places will test those systems for free. My battery light does the same thing, and my alternator is going out. I've got an 06zx4 as well, maybe we've found the lifespan average of the alternator? lol
 
#4 ·
yea i got them checked today, they said there was a dyode bad in the alternator. ive had this car for going on five years, and this will be my fourth alternator iv had to put in.

the battery they said was charging ok but not to its fullest. and my alternator was putting out two or three volts less than it should be. (electrical things arent my specialty so i cant remember the exact things i was told)

im going to go to a couple other places tomorrow to get it checked again just to get a second and third opinion. the battery is only a year old, and the alternator i believe is a year maybe two years old.
 
#5 ·
driving it today it seemed to do fine. seems only at night is when the light comes one, when im having to turn my headlights on. so whatever the problem is my headlights are sucking out the last little bit thats being put out. last night i took my car charger out of the lighter, took the face plate off the radio and dimmed my interior lights as low as possible (with still being able to see) and turned off my air. and the problem still existed. i may go back to walmart and complain, tell them this battery is only a year old and already having problems. depending on the news i found out tomorrow
 
#9 ·
Where are you guys buying your alternators?

It seems to be that cheap diodes are being used in them.

What kind of stereo systems are you running?
 
#10 ·
Mines still the stock alternator (as far as I know, I am the 3rd owner) but I'm gonna have mine rebuilt. There's a guy by my parents house who only does alternators and has for 20 years. He told me that all the alternators you can buy at o'reilys /auto zone /advance auto all use the same crappy Chinese manufacturing and to stay away from them. And I'm just running a Sony head unit, nothing crazy by any means.
 
#11 ·
i didnt really know there was another way to go besides buying them? a friend of the family is a mechanic and owns a shop with his dad, i usually go through him and i get a reasonable discount through advance auto parts. if there is a cheaper way to go about this though please let me know.

my stereo is completely stock except for my head unit. its a sony xplod. (apparently me and matmatician here have the exact same car ;) lol) which reminds me, i put my face plate back on the head unit this morning and went to plug my ipod in, after resetting everything (from disconneting the battery yesterday) my source button wont work on the radio to put the radio in aux mode. idk if its from the battery/alternator issue or just a coincidence.
 
#13 ·
Make sure your battery cables are all solid/intact, especially at the battery clamps. If you have broken wire strands at the clamps then that could be shortening the life of both the alternator & the battery. This happened on our '02 Focus wagon (went thru 2 batteries & 2 alts) & was only fixed after rebuilding the positive cable's battery clamp.

The alt-to-starter cable could also be a candidate for problems, but that cable doesn't usually see the amount of disconnecting that the battery cables do, so it's less likely to be a problem.
 
#14 ·
I have an 01 wagon and I'm getting this now. The Alternator went bad and then the battery so I replaced both, but now the light keeps coming on and it's getting annoying. Any ideas other than those stated? I took it to Orielly and...Alternator passes, battery passes, both are new within a week. This is killing me! Could it be a bad belt or bad tensioner? When I rev the engine it goes off Sometimes...Frustrating!

Thanks in advance!
 
#16 ·
I was thinking about the ECU, but this is wierd...It comes on at low idle or when I'm mid-[range, but when I accelerate sharply it goes off. Could the belt be slipping? Or could there be an issue with the belt tensioner letting the accesory belt get slack? Why would the light go off when I accelerate?

I replaced with a brand new Alt from Autozone, and I had O'Reilly, Autozone and Pepboys all check it and they all said that both the battery and alt were fine...anyone?
 
#17 ·
From my recent experience, the top two suspects for me would be the accessory plug on the alternator (3-wire connector) or the positive battery cable. Oh, make sure you've cleaned the ground connection wires, too. When I had Advance Auto test everything, they told us the same thing: both the new alt & the new battery were fine. Their test equipment simply isn't the right stuff to trace the problem down.

In my case, I replaced the connector first & still had all of my problems. Taking it to an automotive electrical specialist (in this case, an R/V retrofit guy) gave me a way to test the entire system ($80). This provided him the info to determine that the positive cable had enough broken strands that it was killing both the alternator & the battery. He cut off the old terminal clamp & soldered on a new one.

All of our electrical problems were finally solved with that fix. If you don't want to keep guessing, find somebody with the proper test equipment.
 
#19 ·
X2 on testing the whole system, as opposed to individual parts when you've got a head scratcher of an issue.

As I was reading through, I was going to recommend checking the "pigtail" connector & it's wiring as well, because this area USUALLY causes the type of problem you are seeing. It's the communication between the alternator and the ECU, and MUCH more likely an issue than the ECU itself.

The OTHER odd thing seen B4 here was an alternator that passed a quick test, but STILL had a bad diode, NOT too common....

Luck!

P.S. - an easy check to see what's going on with intermittent voltage issues, is to use a cigarette lighter plug to hook a voltmeter to so you can get a reading when the light comes on - sometimes easier than always driving around after setting the car to diagnostic mode so you can see it on the odo display...
 
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