Is My Alternator Going Bad?

[slacktide_bitog]

Does the brake light come on, too? If you see the battery light and the brake light on at the same time, you need an alternator.

 

[JimPghPA]

You wont get stranded. You would have at least an hour to drive after it dies before the engine quits is you don't use headlights or other loads.

Mant years ago that was true. A 2004 will have larger electric loads than a 70's car. Probably more like 20 minutes of run time on battery only. And that assumes a very good battery.

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I looked for some YouTube videos on replacing the belts on that vehicle. Found a 2005. The belts each have there own mechanical tensioner. And 14K miles on new belts could be enough that they have worn in, and now require a slight bit of tightening. Probably still very good belts with a lot of life left on them, but belts do wear in and require taking up slack.

 

[JimPghPA]

I thought a 2004 Nissan would have had self adjusting spring loaded tensioners on it. Mechanical simple screw ones are a cheaper outdated design that most brands stopped using before 2000. But they do work. If tightening them solves the problem, they probably will NOT require a little tightening very often after initial wear in of those belts.

 

[Hall]

I thought a 2004 Nissan would have had self adjusting spring loaded tensioners on it.

Based on what Nissan/Infiniti did with their G35 (VQ35) engines, they were still using screw-type tensioners in those up until 2006. My '08 Nissan (Infiniti) does have a hydraulic tensioner.

 

[Fitz98]

Does the brake light come on, too? If you see the battery light and the brake light on at the same time, you need an alternator.

I am curious why the brake light would come on at the same time.
If it does it again, I will look for that.

 

[Fitz98]

Mant years ago that was true. A 2004 will have larger electric loads than a 70's car. Probably more like 20 minutes of run time on battery only. And that assumes a very good battery.

____________

I looked for some YouTube videos on replacing the belts on that vehicle. Found a 2005. The belts each have there own mechanical tensioner. And 14K miles on new belts could be enough that they have worn in, and now require a slight bit of tightening. Probably still very good belts with a lot of life left on them, but belts do wear in and require taking up slack.

I saw those u tube videos as well. Looks like a little bit of a pain to remove this alternator. The belt still "seems" tight.
I loosened the alternator connector a little (not the big one attached with a nut, the other plug-in one). I wanted to check contacts, but there is a part in the way of removing it and did not have the time to invest into removing it at the moment to check the contacts. I wiggled it out as far as I could and put it back on.
Wife says the light has not come on since.
I am guessing it may be possible the contacts got a little corroded from when my radiator went bad and might have been exposed to some spewing coolant.

 

[Hall]

I am curious why the brake light would come on at the same time.
If it does it again, I will look for that.

I think automakers just do that to increase the odds of getting your attention. One warning light might get ignored, but two ? Hondas have done that for decades, in my experience.

 

[slacktide_bitog]

I am curious why the brake light would come on at the same time.
If it does it again, I will look for that.

Possibly as a warning light to get your attention, as someone else already said. Also to distinguish the problem as the alternator rather than just a low battery

I used to have a 4th gen Maxima, and it had the brake light go on with the battery light. It is likely the same across Nissans of that era.

I think automakers just do that to increase the odds of getting your attention. One warning light might get ignored, but two ? Hondas have done that for decades, in my experience.

I didn't know other cars did that! Though I've never replaced an alternator on a Honda.

 

[Dave9]

If the vehicle was used to jump start another vehicle, AND the vehicles engine was running while the vehicle with dead battery was cranking or trying to crank, then under those conditions, the alternator of the good vehicle could have its alternator output diodes damaged when it puts out a lot of current to try to start the dead vehicle. This sometimes but rarely happens, because the starter of the dead vehicle and the dead battery of the bad vehicle, draws too much current.

This is very rare if the vehicle did not have the engine revved high during the jump start event. If it didn't, there's a finite low amount of current the alternator can output. Old linear regulated alternators typically produce a maximum of less than 1/4th their rated current at idle engine RPM.

 

[Rand]

My 2004 Nissan Sentra battery light flashes on and off occasionally.
It is very random and not very often, just blinks on for a brief moment every now and then. The volt meter is reading 14.4 volts at the terminals.
Is it possible the alternator is just staring to go bad, or should I look to diagnose something else?
I don't want to get stranded with a dead alternator...been there, done that...., but also don't want to waste money.

When does it do it? at idle or anytime?

Alternators usually completely fail, not intermittently like you are describing. If the vehicles Voltage can not stay high enough when the RPMs are low, it usually is that the alternator can not keep up with the demand at those low RPMs because the battery is not doing its share of the work, and even may be draining too much from the alternator.

Worn out brushes can cause intermittant failure. Seen it a few times.

Otherwise if its a cheapo aftermarket alternator.. those can have issues and be junky.

 

[davea180]

My 2004 Nissan Sentra battery light flashes on and off occasionally.
It is very random and not very often, just blinks on for a brief moment every now and then. The volt meter is reading 14.4 volts at the terminals.
Is it possible the alternator is just staring to go bad, or should I look to diagnose something else?
I don't want to get stranded with a dead alternator...been there, done that...., but also don't want to waste money.

I used to have a 2004 Altima. The flashing battery and sometimes the brake light also indicates a bad alternator. Easy fix but would not recommend anything Carquest for this.

 

[eljefino]

If your ABS pump doesn't like low voltage it might set its light off... and there are trends to light the "BRAKE" light as well if the ABS fault is "important enough."

You have an internal alternator problem, probably bad brushes.

If you're running the HVAC blower motor you'll hear it change frequency in relation to the dips in voltage. Human ears are very good at this. Headlight flickering is also noticeable.

 

[kc8adu]

on 6 gen hondas if voltage is low or high all the door warning lights also come on.

 

[Snagglefoot]

Over the years, I have changed out a few alternators. They all gave a few flickers on the warning light. That was enough and I pulled them out. The latest one to do that had over 200,000 miles. In each case, no more flickers after changing it. In the last case I also had a voltmeter and it was wandering. It also gave a “check charging system” message. After the change it was steady.