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Old 03-29-2011, 04:42 AM   #1 (permalink)
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Default alternator problem or ecu problem?

Hi I do need some help here, my car is 2004 mazda 6 luxuy sport GG1 .. 122000km

My carís battery light has on for few weeks, I have been to few places and they told me that they been tested my battery and alternator and they all work just fineÖ.and other guy told me my car is may be ecu problem, he tried to reprogram it but cannt so he said I should change a ecu because ecu said alternator no charging but itís actually charging so it could be ecu problem.

I have been drive my car with battery lights on for a month everything is fines nothing wrong at all but battery light never goes off. ( it actually goes off for a week and come back again)

So I went to Mazda service station yesterday to do full inspection and they keep my car over night charge me a lot of money and finally said the problem is alternator which will cost me 1000 dollar to do it ( btw I come from Australia, I cannt believe why alternator is so expensive here) ..

I have got report from them said:
Checked and confirmed battery light on. Checked and found code logged in system. Cleared code. Tested, code came back. Check drivebelt for tension/wear, all ok. Inspected wiring connections at alternator and at PCM, all ok. Tested wiring loom for shorts, none found. Tested for open circuit. None present. Tested alternator readings at PCM and alternator below specification. Need to replace alternator.

So my question is that my carís problem really is the alternator break down? Or something wrong with connection? I know I shouldnít doubt Mazda service station because they made this car but I just wanna know ..


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Old 03-29-2011, 10:02 AM   #2 (permalink)
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it might be the alt. it kinda sounds like it. Im just surprised that it not doing the whole shutting the car down while driving like most ppl have happen to them. But then again i guess its charging but maybe not fully charging the batt and it is throwing that light. I would replace the alt. they not to terrible to do. you gotta get under the car and get it from down below. Im sure someone here has a write up on how to do it. The alt itself is not ecpensive i think mine was like 80 bucks i might be wrong though its the labor they raping you on. But its not uncommon for the alts in these cars to go bad I hearits a common problem your just lucky it not cutting off on you while driving down the road like it did me.
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Old 03-29-2011, 12:31 PM   #3 (permalink)
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start the car and put a multimeter on the battery and see what it reads. This will tell you real quick if the alternator shit the bed or not.

Alternators are cheap, having them rebuilt is even cheaper........ the labor however can be very costly.
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Old 03-29-2011, 03:32 PM   #4 (permalink)
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hey, thanks for reply ...

I got someone who is going to rebuild my alternator for cheap price..I hope this problem will finish soon ...

and few service station ppls already did to test battery by multimter and all the result were good..so that's why they have no idea what happend and end up me have to go Mazda servise station to do full test (god! they r damn expensive) .. is it normal?? I still have to drive my car with battery on for at least a week...hope not break down during this time ...
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Old 03-29-2011, 04:34 PM   #5 (permalink)
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Something else is wrong. this doesn't sound like an alternator issue.

what readings did they get when the car was running voltage wise?

the alternator is not a "sometimes, but not always" part....... it is either functioning properly or it isn't.

other than the dash light, what other issues are you having? a multi-meter should be all that is needed to diagnose this. both from a wiring issue to a alternator issue.

Ps have you tried simply reseting the car and see if clears the battery light? Does your car currently throw any codes when hooked up to the OBD2 reader?
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Old 03-30-2011, 12:47 AM   #6 (permalink)
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when I start my car, all the dash light is on(i think this is normal) and after that all dash light disapper except handbreak light, after a while battery light coming and never disapper...(but sometimes the battery light goes off for a while(like a 20 km trip) but it not often happend)

oh btw, when the battery light coming for the first three days nothing was worng, after three days the battery light off for a week but I did feel sometimes when i try to start the car battery go flat becasue it takes more time to get start ..after a week the light came back again until now..

my car also takes more time to get start last week but I just think the wealther was too hot ...and for the reading in my car to show estimate average fuel consume for km, it did go worng for a while but after I reset my ecu all become normal .... that all so far.

I did try to reset ecu but battery light always come back..and sorry I dont know anything about OBD2 reader or somthing that's reason why i have to go mazda service station to see what happend..becasue
I really feel nothing wrong with my car expect the battery light on..

the guy going to rebulid my alternator said if my rebulid one doesnt help I may have to change my ecu ... is that possible? I dont really think computer can easily go worng ..

thanks for the reply ..

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Old 03-30-2011, 08:41 AM   #7 (permalink)
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i remember reading something about the charging system on the 2.3's being goofy. you have to reset something anytime you unhook the alt, or it starts doing what your having issues with. it was brought up, and mentioned in a thread like a month ago. search "alternator" and read the threads that come up. i know this has been mentioned.
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Old 03-30-2011, 12:53 PM   #8 (permalink)
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Just throwing this out there. I had similar issues when my alternator went bad. When it alternator crapped out on me I took it to Napa, Autozone, Advance, and Pepboys was the only place that had the right equipment/connectors to check it. They told me it was good.

The clerk at AutoZone told me that it was most likely that my alternator was not good and not outputting the correct voltage.
I replaced it and have not had an issue since.
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Old 04-09-2011, 04:42 AM   #9 (permalink)
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I have reconditioned my alternator a couple of days ago, but it seems the guy work on my car didn’t fix it alright, the battery light still on sometimes.

The guy keep telling me that in his experience this problem usually caused by ECU but his customers always try the cheapest option first… so now he said I need to change my ECU..

BUT I doubt what he said, because after I droved my for a couple of days I find it bit different than before. First, when I drive in the day time without turn on the aircon the battery light never show up, but if in the night time with head light and aircon on the battery light will on. Second, if I start my car and turn on aircon straight away the battery light will on but if I drive a few km than turn on aircon the battery light wont show up ..

So I have my test drive result, as long as I don’t turn on my head light and aircon at same time or don’t turn on my aircon my car’s battery light will always off …and again the same thing even thought battery light is on but my charging system still function. But the guy told me because Mazda6’s ECU controlled everything so if I don’t fix the ECU my battery will always undercharge when battery light is on.

Is anyone know anything about this? I am actually think that the guy who fix my car try to cheat on my so he didn’t fix it properly but ask for more money to fix my ecu.. Because he actually try to ask for more money to do the job but I didn’t accept it.

And if it is ECU problem how come MAZDA service station didn’t know that? ..
If it is actually a ECU problem is that possible to have same case like my problem??
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Old 04-09-2011, 10:32 AM   #10 (permalink)
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Quote:
I know I shouldn’t doubt Mazda service station because they made this car but I just wanna know
I lol'd at that
Quote:
And if it is ECU problem how come MAZDA service station didn’t know that? ..
If it is actually a ECU problem is that possible to have same case like my problem??
mazda alternators dont have a internal regulator; the ecu takes the function and controls the field coil. So yes it could cause the problem. It's trivial to check if the ecu is doing this correctly with an oscilloscope and and looking at the field coil control signal (in fact the correct waveform is given in the workshop manuals)

Quote:
I have reconditioned my alternator a couple of days ago
It's usually better just to replace. Anyway if you know how to do basic car work take the alt down and bring it to autozone or advance or something similar and they will test it for free if you dont have the equipment. edit- I just read javs post... maybe they cant do it then :P
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