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Discussion Starter · #1 ·
I have a no-start condition with my Mazda6 Sportwagon that I believe is due to electrical issues and need some help narrowing down the root cause. My car is stock. No electrical or any other type of repairs have been performed in the past six months.

I drove home from work on Friday night without any issues. When I went to go start the car approximately 30min later, it would not turn over. Specifically:

With the key in the ACC position, only the door open warning lights up. None of the other warning lights illuminate. With the key in the start position, nothing happens. I don't hear the fuel pump prime, and the engine does not turn over. If I then turn the key to the off position, I can hear the Bose 6-CD player cycle. The needles on all the gauges (odometer, spedometer, fuel, temp) will then turn all the way clockwise and bounce off the hard stop without any of the lights going on. Headlights, foglights, and brake lights are inoperable.

I've checked the battery and it has 12.96V. I've also checked all the fuses and none of them are blown. A quick search of the forums (+electrical +problem +start) did not yield any similar problems.

I'd appreciate any ideas or suggestions as to what the problem might be.

Thanks in advance.
 

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dont think jumping it would do anything because the battery has a charge...Hmmm

what's left>>>>???

1) Alternator? not holding the power from the battery...
2) Starter? Do you hear any noise when you turn the key to the on position? do you hear the infamous "click" sound from around the passenger side dash...?
 

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check and tighten the bolts on the power connections to the main fuse box in the engine bay. that might help, might not. seems like somthing might be loose if its intermittent.
 

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Discussion Starter · #5 ·
First of all, thanks for the helpful responses. Here's an update on the issue:

I double checked all the connections that I could find under the hood and none were loose. I tried to restart the car and did not notice any sound from the passenger side of the dash. I retested the voltage at the battery, and it was 12.7V with the key in the off position, and 0V with the key in the accessory position.

To me, that indicated a problem with the battery. I was able to jumpstart the car from my wife's CX-7, and after checking to make sure that the battery warning lamp was not lit, I drove it to the dealer for servicing. Once parked at the dealership (a 2 mile drive), the car would not start up and displayed the same symptoms as listed previously.

The dealer confirmed that the battery was not holding charge and replaced it. However, they also discovered that the alternator was putting out 16 to 20V instead of the normal 14V. A new alternator is on order and will hopefully be installed today.

I was thrown off by the failure mode of the battery. All of my previous cars (95 SHO, 02 Jetta) displayed dim headlights, long/ slow cranking, etc as the signs of battery failure. On this car, the issue was that the computer was not able to draw enough juice out of the battery and as a result, the dash went haywire.

Thanks again for the responses. Hopefully, I'll get the car back from the dealer this afternoon and I'll update this post with a final root cause. I still need to ask the service manager why the battery warning lamp was not lit when the alternator was putting out > 14V.
 

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it probably didn't show the battery light since the alternator was giving it enough voltage to think everything was fine. The regulator went in the alternator, afaik that is the part that controls output voltage.
 

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Discussion Starter · #7 ·
I picked up the car this afternoon. The service manager told me the root cause of the battery failure was the alternator overvoltage, so they covered the cost of the battery replacement under warranty instead of pro-rating it.

He didn't know why the overvoltage condition didn't cause the battery lamp to light up. . .It was probably for the same reason that dream weave mentioned. . .However, he was surprised that it didn't throw a code. . .

At least I learned a lesson about the failure mode for batteries on this vehicle.

Thanks again to everyone for the support.
 

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However, they also discovered that the alternator was putting out 16 to 20V instead of the normal 14V.
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I thought the alternator was supposed to produce 14.5V, not 14.0? My own lights are dimming noticably and mine's producing 13.8V. My meter only has a 10A circuit, so I'm unable to test amperage, but unless the 6 is different from every car I've ever owned, my alt is down .7V. My batt is only reading 12.3V after sitting overnight in 30 degree weather, so I'm guessing I'll end up with a dead batt soon if I dont replace the alt.
 

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Better get a new batt or no more cruisin for hot guys
 

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This JUST happened to me. I'm going to go back to my car now and try to jump it. Didn't even think to try that due to the behavior. Definitely atypical of any battery issue I've heard of on a car.
 
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