Low battery causing radio issues?

[Mursilis]

Test drove an '04 Miata over the weekend, and when the owner went to pull it out of the garage, the battery was dead (didn't really use it over the winter). He had to jump start it to get it going, and then we took it out for about 15 minutes. I was testing out the radio, and the volume kept flucuating - normal levels, then sudden drops to nearly a whisper, then back up, etc. This issue appeared no matter the source - playing both FM and a CD in the head unit resulted in volume issues. The owner claimed he'd never had an issue with the radio before. Could the problem be related to the low battery level, or something else?

 

[iamwiz82]

Have him charge the battery and then test drive it again. That'll be the easiest solution.

 

[StageLeft]

Originally posted by: iamwiz82
Have him charge the battery and then test drive it again. That'll be the easiest solution.

Yep.

I suppose it's possible if the battery is completely dead, but the alternator should be keeping its volts pretty steady and at a good level once you've been driving, even if the battery is really low on charge. If the lights and all that were fine it doesn't terribly lend itself to the idea that a weak battery could be doing this.

 

[LTC8K6]

Related to the jump start maybe...possible surge damage?

Low voltage problems should be doing more than just making the radio volume change.

With a good alternator, once the engine is running, you don't need the battery at all.

 

[Mursilis]

Thanks all - I figured the issue was unrelated to the battery problem. It seemed to be the door speakers going in and out on the car, and I've heard they can be problematic due to poor weather-shielding.

 

[Zenmervolt]

Getting the door panels off a Miata isn't that bad. You can put new speakers in without much difficulty.

ZV