Hi Guys,

I noticed both my battery and brake dash lights went on simultaneously for a few seconds. It happened a few times recently, however I can drive for hours on end and they stay off.

I read through the posts here and most say it's the Alt. I went to Auto Zone and had them check it out. He said the Alt was checked out fine, but the battery might have a weak cell. I didn't press him on what he meant ( my fault) but it is 6 years old.

I also did a check myself on two different days. I connected my multi-meter to the battery terminals and got the following readings.

Engine off - 12.92
Engine on (no-load) - 14.34
Engine on with headlights, blower, read defrost, ect - 14.10
Right after shutting engine off - 13.32

So Auto Zone saw no problem with the alt, and neither did I (at least from the two tests I did).

My question is, where do I go from here ? And would both Brake & Batt lights go on simultaneously if the problem is the battery (dead cell) instead of the Alt ?

Thanks.....

 

The lights tell you that the alternator is not charging. You evidently have an intermittent problem as the lights go off. Check that the alternator belt is tight and in good shape - i.e., not cracked and or missing sections of the ribbed portion.

The battery (good or bad) does not play any part with the light. You can remove the battery from the car and the light will not come on as long as the alternator is charging.

The voltages you posted are exactly what you want for those measurements.

 

Check over your alternator. Something isn't working the way it should be. Maybe you have a poor connection, bad wiring, even the pulley could be causing the intermittent charging situation. Regardless, something related to the alternator is causing those lights to come on.

 

There is a small wiring harness with a plug that plugs into the alternator. Carefully check the plug connections as I've seen the plugs break over the years.

Depending on where you live and the amount of salt exposure, there is a possibility the plug connections could get corroded.

Here's a picture of the alternator wiring harness. I've had to replace one over the years.

 

Thank you for your help guys. I'll try to get under the car and look over the Alt and connections tomorrow or the next. Hopefully it's just a bad connection. If not I suppose then I should replace the alt as it might be on it's way out.

This is a great site btw, always good advice from knowledgeable people....

 

How old is your battery and where did it come from?

I have seen a shorted/weak battery create alternator issues. Usually the alternator completely stops charging and then I replace it. Then I find I have a problem battery. So I end up replacing an alternator and a battery.

About 10 years ago I started proactive battery replacement at 40 - 42 months for batteries that are sold as 36 month full replacement / 5 year pro-rated replacement.

For the cars where I didn't miss replacing the battery at 40 - 42 months, I've never had an alternator issue. For the car where I forgot about it and went over 46 months, I got to replace the alternator and the battery.

For one of my cars, replacing the alternator is a very long and painful process. In fact that one is due for a proactive battery replacement right now.

A healthy battery = a happy electrical system.

 

CS_AR,

My battery is about 6 years old, I purchased it from my local Auto Zone. As I mentioned when I brought the car to AZ to check out the Alt, they told me the alt checked out fine (as did my tests at home) but the battery may have a bad cell. I didn't press him on the 'bad cell' which was my fault, but I did intend to go to two other stores in neighboring towns to get a second and third opinion on the alt and battery.

However it seems from the responses here that if the lights go on - even briefly - the problem is the alt and or connections and not the battery. So given that I thought I'd instead focus on checking the connections and retesting the alt myself and ultimately replacing it if I can't locate any fixable problems (loose connections, ect)

Is there a possibility that the battery is causing an intermittent problem in the alt which is causing the dash lights to come on, and if so should I first change the battery and see if that corrects the problem ?

Or is the problem just with the alt and I should forget the battery for now ?



Again, I could drive for hours and the dash lights will only briefly flash on for a few seconds. One day I drove all day with the lights never coming on.

 

I would check the connections first. That doesn't cost anything.

The last time it happened to me, I had to replace both the battery and alternator. It ran and started fine until the alternator stopped charging one night and the car died on the road. I replaced the battery to get the car home that night to avoid a tow charge. Since I could tell the alternator was not charging by using my multi-meter, I really knew I had a bad alternator.

I didn't think the battery was bad so I kept it and tried to charge it using my home charger. The charger indicated the battery had a short. I took it to AA and had them test it where they found a bad cell.

If it turns out that you need a new battery after all, I get mine from AdvanceAuto.com and use the TRT41 online discount code for $40 off. That puts the cost in the $96 range. I usually order batteries online to get the discount and specify pickup at my local store. The AA people install the battery when I arrive to pick it up.

As for alternators, me and people I know have had good luck with Bosch rebuilt on the 4th gen from NAPA.

As DennisMik pointed out, a bad battery doesn't cause the light to come on.

 

Today will be the fourth day and so far the dash lights have not come on !

I did check and clean the alt a few days ago the best I could, as I could hardly even get to it. (not the easiest car to work on) It did have a lot of oil on it, I sprayed the connections with WD40. I also installed a new battery, since four out of four Auto Zones and Advanced tested and said it was on its way out.

I'll keep an eye on it but for whatever reason so far no problems. Though winter is on it's way, and the first sign of trouble, out it comes.

Thank you all for your help !

 

It is good to see things are working out for the better. As a side note, I belong to another car club that has a fairly large number of members from North Dakota, Maine, Minnesota, Canada, and Newfoundland. I got an education about Cold Cranking Amps (CCAs) and how a weak battery can shorten starter life and wreak all kinds of havoc with a vehicle's electrical system. They are very much into proactive battery replacement. They don't want to be left stranded in extreme weather conditions by a battery that is past its expected service life.

 

With a 6 year old battery, I doubt that it will make it through a cold winter. I suggest that you replace it now before you find yourself stranded with a car that won't crant.

 

Thanks for that, I was a little hesitant but after reading the responses here I thought it best to be proactive and replace it. I'll be doing the same for our other car as well. Pricey but worth it.




Yes, I replaced it a few days ago. Hopefully it will get me through the winter. I still have to keep an eye on the alt though...