While driving to visit my family tonight, the charging system indicator light came on (battery symbol). Fearing a serious alternator problem, I pulled over and called triple A. While waiting for the technician to come, I restarted the car and guess what? No battery light!
The triple A guy hooked my battery to his voltmeter with the engine running. It held steady at 13.5. This suggested the alternator was working as the battery was holding a charge. I decided to try and reach my destination.
2 miles later the light came on again. Restarted, and it was off. Drove another mile and it came on again.
I took a chance and managed to drive 25 more miles to reach my parents’ house. The battery light remained on the whole time.
I want to go to a shop tomorrow to have it checked out. What should I ask him to test or check out? Any thoughts on what the problem could be?
You need to have your alternator output checked. The light can come on intermittently as the alternator starts to reach the trigger point to turn the light on. It doesn’t necessarily have to be linear or do it all the time. Sometimes the light just barely comes on but in any case it signals a charging system failure or related like loose belt, bad connection, etc. Don’t keep shutting the car off and starting it again though hoping for self-healing. Every time you do that you are depleting what little reserve the battery may have left.
I think telling the shop your experience, should be sufficient, given the number of possibilities. If they are good, a hands on will be better than any of our guesses.
If I am close to home, I turn around. Might make it home. 1/2 way to destination? Keep driving. Unless your route is thru heavy congestion and/or major traffic issues if you stall. Keep going.
I suggest the highest quality part, versus some bargain part with a lifetime warranty
You want to just replace it once, not frequently, each time paying for labor
I remember a guy that bought a cheapo store brand alternator with lifetime warranty. Every year, he’d have to swap it out for another one. Sure, HIS labor was free, since he did the himself, but it was a major hassle. And he’d have to head to the store in another vehicle
This could be as simple as the serpentine belt being oily, and the belt slipping.
Or the serpentine belt tensioner could be not keeping the belt tight enough for it to turn the alternator ads fast as the engine is running.
Bring a volt meter with you, and when the light turns on pull over, keep the engine running, and measure the voltage at the battery. If the battery light is on with the engine running but the voltage at the battery measures 13.5 volts or more, the problem is the battery light circuit, not the alternator.
In most cases the battery light turning on doesn’t mean that there is a problem with the battery; it means there’s a problem with the alternator or charging circuity. If you want to be pro-active, It’s a good idea before winter sets in to do a proper battery service and check the charging system. I did that job a few days ago for my Corolla b/c it was getting a little slow to crank. Removed the battery and cleaned top and bottom & all sides with a weak solution of baking soda and water. Next I removed the cell caps and checked the fluid levels. Then I cleaned the battery posts and connectors with a battery cleaning tool. On reinstall I noticed one of the connectors wasn’t making a super-tight connection to the post so I filed a little metal off the connector ridge so it would tighten against the post better. Then I measured the battery voltage without the engine running to confirm it was about 12.5 volts. Then I started the engine and confirmed the battery voltage measured 14-15 volts, and gradually dropped as the engine warmed up and the battery charged. I also noticed the slow cranking problem was solved.
Just as a guess I would say that the brushes inside the alternator are causing the intermittent problem, especially if there are no loose connections found being the cause of the trouble. If the alternator is the same one since the car was new then it is a pretty safe bet that it is most likely causing the problem. It has gotten a lot of use. If the battery is questionable it would be wise to replace it at the same time since the two work together and problems with one can also effect the other.