Good morning/afternoon,

Please forgive my ignorance concerning cars, as my current 2008 XJ8 was my dream car. Nevertheless, during a recent road trip, the battery light came on. I was able to complete the remaining five hour drive home (sitting on pins and needles). Upon pulling into my garage I noticed my fan was noticeably loud and a slight whine as I accelerated. Car cranked up fine the next morning, but the whine and fan was noticeably loud again. I checked the batter cables in the trunk (new car battery) and noticed no corrosion or gunk, but did notice a green and yellow/orange wire that was not connected.

Any help or advice is welcomed and appreciated.

Battery light and fan noise may or may not be related. For the battery light, put a voltmeter across the battery terminals to see what the voltage is while the engine is running. It should be over 13volts (typically 13.5 - 14.5 depending on the state of the battery and assuming a fully functioning alternator). If it is less than 13volts then the prime suspect is the alternator.

Thank you!

Alternator failure is the most obvious. For my peace of mind, I have a plug-in voltmeter for a cig lighter socket, just a few bucks on Aliexpress or undoubtedly available locally.

The voltmeter can be confusing. For instance, the alternator should certainly put out 13~14v or more for 5 minutes from startup, but it may then "cut-out" for a while depending on the need. Anything in the 12v range is "not charging", but as mentioned it will always charge for 5mins from startup.

Alternators do pack up. In my case...on the Honda. Whew.