Wondering if an old serpentine belt could cause a battery light? Had a battery light pop up on the car and figured it was the alternator, (battery not even a year old and tested) went to a shop that specializes in batteries and alternator rebuilds etc. They said it tested bad and the housing was cracked. Installed the new part and still have the battery light. Here's why I didnt want to replace the belt just yet. I was planning on taking the car in for a timing belt change in a week or 2. 20 year old car on what I believe, could be wrong, but I believe is the original timing belt considering the car only has 85k miles on it. They replace the drive belt, timing belt, water pump, coolant for the package price. Didn't really want to buy a 30/40 dollar belt when im paying for that with the timing belt swap a week later. So if i can get it up to the shop with the battery light on, im hoping when they replace the belt maybe the light will go off? Or it could be a faulty alternator. The belt is definitely old but its spinning. Would that still cause a battery light?

 

Could be a lot of things including the old, worn out belt or the tensioner. FWIW, I think your plan of attack makes sense. If it were me, I would throw a new belt at the problem and see if it goes away since belts are cheap and easy and you know it's old. But if you're not a DIYer and the belt's getting replaced soon anyway, then it might make sense to wait. It all depends on your risk tolerance. A broken serpentine belt will leave you stranded. Is this your daily? Can you park it until your timing belt appointment?

 

belt and belt tensioner in tandem would be my next two replacements

 

Oh yea it can be parked for sure. Its been sitting for 4 months because the battery light came on and the car died. Its been cold and I just got around to changing the alternator this weekend lol. I was thinking about throwing a new belt on it myself but since im paying for the timing belt package I think I can make it on a fully charged battery with my wife following. The shop is using OEM parts. I just didnt wanna spend an extra 30 on a belt thats about to be replaced in a week. Unless I could get it back and return it lol. Its not like theyd knock off 30 bucks if i told them i already replaced the belt... My biggest fear is they do all the work and the light remains then the shop will try to feed me crap about it. I got a life time warranty on the alternator that I literally just bought and installed a day ago. Im hoping its not that and then ill have to redo it but whatever. The belt is super old though. Im hoping that set off the battery light. Which makes me wonder if it was the alternator at all ha.

 

It's not too hard to test your alternator output with a cheap multimeter. If you get normal voltage at battery terminals, you can rule out bad alternator and belt. If you do not get correct voltage at battery, then I'd test output at the alternator directly (little harder than 1st test but nothing compared to installing the alternator). If you get correct output at alternator, then the problem is the cable or connections between alternator and battery. Good luck.

This is pretty comprehensive from etcg.


My first multimeter was a cheap craftsman I got for 10 dollars. It wasn't very accurate, but good enough for 90% of car stuff, and it didn't hurt when I broke it by testing voltage when I left the selector on resistance.

 

yea i tried that and my battery wasn't getting a charge so I replaced the alternator. Shop said it tested bad so figured that was it.. installed and still getting a battery light. Hoping its the old serpentine belt now.