Rattling noise under hood, then battery light

[nicole2525]

Hi All, I was just driving home and everything was running fine until I was about 3 miles from home. I heard a rattling noise that kinda sounded like it was rocks rattling in the wheel well. It got louder and sounded like it was coming from under the hood. After about 15 seconds it stopped and then my battery light went on. I made it home, turned the car off and back on again, started up like normal, and the battery light is still on. Any thoughts on what could be causing this?

Edit: 2015 Mazda CX-5 with ~83k miles

 

[RedBaron]

Check your belts. You might have lost the alternator belt. Do NOT drive it if so, or it will strand you.

 

[HyFlyer]

+1 on the serpentine belt broke/came off. Besides the alternator, it also runs the air conditioning compressor so that's out too. To check, standing in front of the car with the hood up, look to your left (passenger side) of the engine and you'll likely notice the main belt missing. A little farther down, you should see a single thinner belt for the water pump. Hopefully that's still there.

The good news is, the accessory serpentine belt is not too involved to replace. Whoever you have replace it (or yourself if you DIY) have them replace the tensioner pulley and water pump belt as well while your in there.

If you need to take it somewhere for repair, if it's close you could drive it but you have to make sure the water pump belt hasn't been damaged. It can run a short distance ( less than 10 minutes or so) if your battery is fully charged and in decent shape without the alternator turning but I wouldn't risk running the engine without the water pump working. Safest is to fix it where it is or tow it if necessary. If your not sure, don't run it. That could turn a simple fix into a major problem.

 

[nicole2525]

Thanks everyone for your input, it was the alternator belt. Water pump belt was fine and we were able to drive it to the shop.