Battery light indicator on 2003 P5

[Mazdagirle1]

I have a 2003 P5 with about 40,000 miles on it. For the past 10 days when I start my car in the morning the battery light indicator lights up and stays on for about 10-15 minutes. It does the same thing after sitting for several hours. The car doesn't stall and I have no problem starting it up. I've been back and forth to my mechanic who tested all of the circuits and replaced the battery and the alternator. Within a couple of hours of having the battery and alternator replaced, the light was back on. He checked everything again and said that the only circuit he couldn't check was the computer and he suspected that it was the engine control module so he sent me to the dealer (and he put my old battery and alternator back in and refunded my $$ ). The dealer checked it out yesterday (although they didn't even listen to my list of "symptoms" or what had already been checked) and said it was the battery and alternator and wanted over $600 to replace both! I know I can get a battery for about $80 and an alternator for about $200 and I know its not a hard job if you have the right equipment so that was a lot of labor tacked onto that cost! So I took the car, bought a new battery and replaced it myself. It was fine when I drove it home from the autopart store, but this morning the battery light was on again. This morning its at another mechanic (the third!) to have the alternator looked at. I'm getting really frustrated and I don't want to be damaging my car by driving if its something serious. Has anyone else run into this problem?? Any advice??

 

[SocialStealth]

Do you have any modifications on the car like a stereo system that might be drawing power?

Maybe its a short someplace. You could try taking the gauge face off and check the wires there.


40k miles and theres no type of warranty? where did you get this car?

 

[Shadow102]

I know the alternator regulator circuit is internal to the ecu so your first mechanic may be on to something. The only other thing I could possible thing of is a bad connection between the alt and battery.

 

[i12drivemyMP5]

How bout welcome aboard, can we get pics & good luck tracking that peskiness down. Cables, wiring & ecu check as was stated would be next IMO.

 

[TheMAN]

checked the intake temp sensor?

 

[slavrenz]

Do you have any modifications on the car like a stereo system that might be drawing power?

Maybe its a short someplace. You could try taking the gauge face off and check the wires there.


40k miles and theres no type of warranty? where did you get this car?

A lot of warranties also have time limits in addition to mileage limits. Not sure a 6+ year-old car would still be covered by even the factory warranty.

 

[slavrenz]

Did you not trust your first mechanic? If you said he already did the battery and alternator, why would doing it a second time fix anything? Have you checked your alternator belt? Maybe it is really loose or something and is not turning the alternator properly.

checked the intake temp sensor?

How is the intake air temp sensor related to the charging system?

 

[detroitcity]

I ran into a similar problem recently.

I replaced an alternator and battery only to discover the same problems I was having before the big switch.

The problem... the alternator I bought from Autozone was bad. So i basically wasted an afternoon by putting in a defective alternator.

The alternator could still be bad.... and if the dealership says that it is, it might very well be.

If I were you I'd buy an OEM alternator and install it yourself. The job isn't too difficult if your confident with cars.

If that doesn't work, then it could be a problem with the ECU, which would severely suck.

 

[flash75]

Has anyone checked the voltage out of the alternator when the light is on and the engine running? A simple voltage check with a multi-meter should read around 14-14.5 volts if the alternator is good. Most garages should have a battery tester to check the battery. Since the regulator is in the ECU the alternator could still be good if the problem is in the ECU.

I wouldn't trust the dealer that told you both the battery and alternator are bad. That rarely happens. They should do a little trouble-shooting to locate the problem instead of replacing everything that could cause the problem.

Perhaps your original mechanic did enough trouble shooting to learn the regulating signal is missing from the alternator input. But you have to wonder why he decided to replace the battery and alternator.

Clifton

 

[gus5]

First of all, that's awesome that the first mechanic put the old alternator back in and refunded your money. Quite shocking really.

The second alternator could have been bad as well, but it's really easy to check as others have indicated. If the voltage regulator is in the ECU, then you might need a new ECU. They're usually in the alternator and they're usually what goes bad when an alternator fails.

 

[i12drivemyMP5]

This is also why there's a sticker on new alternators stating that it cannot be tested out of the vehicle. Hoping this wasn't the case here.

 

[smittyp3]

Me Too!!!!

I have a 02 protege dx 2.0. I had the same problem 3 yrs ago and went thru 4 Premium Bosch alternators before I got one that lasted more than a couple of days. 3 days ago it started again. Im a mechanic for a living( but not very experienced in electrical). WHAT THE HECK?????. Im just as baffled as well. I did notice after the light came on , I checked the belt tension. It was GUTENTITE as anyone knows these belts have to be to not squeel. Next I checked the battery terminals. Tite and clean. Next I reached down and unplugged the connector on the alt. itself and cleaned a little bit of gunky Dielectric grease out and wiggled the connector on its plugin . After that. It seemed to be fine, but came back on today. Also, 3yrs ago I went as far as testing the continuity on the regulator wire to the ECU and pulled it out and cleaned and lubed all the plug connectors on it. Then went through another alternator and that seemed to fix it at the time. Im sure it is either an ECU problem or a short somewhere. The computer is mounted on the floor under the passenger feet and Im sure that it is very possible that during Rainy conditions here in Florida and 3 yrs ago Late fall in Idaho at the time that water might have something to do with it.

 

[slavrenz]

I have a 02 protege dx 2.0. I had the same problem 3 yrs ago and went thru 4 Premium Bosch alternators before I got one that lasted more than a couple of days. 3 days ago it started again. Im a mechanic for a living( but not very experienced in electrical). WHAT THE HECK?????. Im just as baffled as well. I did notice after the light came on , I checked the belt tension. It was GUTENTITE as anyone knows these belts have to be to not squeel. Next I checked the battery terminals. Tite and clean. Next I reached down and unplugged the connector on the alt. itself and cleaned a little bit of gunky Dielectric grease out and wiggled the connector on its plugin . After that. It seemed to be fine, but came back on today. Also, 3yrs ago I went as far as testing the continuity on the regulator wire to the ECU and pulled it out and cleaned and lubed all the plug connectors on it. Then went through another alternator and that seemed to fix it at the time. Im sure it is either an ECU problem or a short somewhere. The computer is mounted on the floor under the passenger feet and Im sure that it is very possible that during Rainy conditions here in Florida and 3 yrs ago Late fall in Idaho at the time that water might have something to do with it.

Bosch products are crap IMHO, buy a different alternator.

 

[i12drivemyMP5]

How is the intake air temp sensor related to the charging system?

There are at least a couple of seemingly non-related goofy connections in these cars. If he asked, there's a good reason. I'd check it.

 

[hoanmy]

Did you not trust your first mechanic? If you said he already did the battery and alternator, why would doing it a second time fix anything? Have you checked your alternator belt? Maybe it is really loose or something and is not turning the alternator properly.



How is the intake air temp sensor related to the charging system?

Do you have an aftermarket intake? I bought my car with an intake installed and over time the wires to the air temp sensor got severed. This caused the battery sign to come on randomly and when i accelerated. You'll know when the wire are completely severed when the battery sign stays on. Try to take your air filter off and check the air temp sensor. It looks like a plastic slender cone. goodluck

 

[nickster]

LOL... I bet it's a pesky ground wire not getting a good connection. After 10min or so, the light comes on; that's about the same amount of time it takes the engine to get hot. When wires are hot, there's resistance. A bad connection + heat resistance = a lit battery light. Good luck and welcome to the forums!