Hello,
I got a red battery light on my car's dashboard yesterday while on my way to Walmart grocery shopping and for some parking reasons, I wanted to restart the car immediately after stopping. Shockingly not only the motor couldn't start but was completely dead with no sound. With my being far from home and during a weekend, I rushed to the Walmart automotive department to ask their advice. They tried to restart the car (charge the battery) but she did not retain the charge. Therefore I had to buy a battery H-7 type from them and the car started nicely. But as the battery light was still on I asked them why was that and they said that the "system had to reset itself". I got home without any problem beside the light and reset my clock and radio but the red light stayed on. I did some internet search about the causes of the this light and found. that just some wiring could have been the cause including of my dead battery. Really? Shouldn't I have replaced my tagged by dealership (oh, ah) "jaguar" battery 6 years ago (I didn't even ask my Jaguar battery back) What should I look for just for the sake of not worrying? But if my car runs okay how can I get the little red light out of the system? Thank you.

 

Marcela, I sent you an e-mail with what I would try first. In short, you are going to start the car and turn on everything electrical. After a few minutes, if you have a bad battery cable, the bad cable will start to get hot. In some cases, it can get VERY!!!! hot. So, like I said, cup your hand OVER the terminal. Lets see what you have with this check and then go from there.

 

Hi Marcela, if the battery totally discharges again then it is your alternator. A red battery light on normally means it isn't being charged and that means alternator.

 

You are right, Nasherman. It was the alternator, but unfortunately because I did not know it at the time, as my car died during the weekend while shopping at Walmart, my (and of the Walmart "mechanics"') only choice was to change her battery. On the following day she died again while running (of course with a red light battery icon) so I had to tow her to the local mechanic, who told me what you say, making me to buy a new alternator after testing the alternator.she had --that was also bad!-- But then it was too late, I did not have my most probably still okay jaguar (interstate) H7 battery anymore but a Walmart H5* one which complicated the things even with a new alternator which simply refused to charge it. So my ignorance cost me a new alternator, a new battery (as the Walmart's H5 did not accept the charge from the even new alternator which courteously rejected it as well and the mechanic provided me with an interstate H7 instead), towing, and.3 hours technician's work. With my pocket burnt badly but with a car running nicely. Good to know next time.
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I only discovered that Walmart lied to me that they installed an H7 battery not H5 that they did on the following day after returning from them.

 

That red light indicates an issue in the charging SYSTEM, not necessarily in the battery itself. The most common cause of that light illuminating is not an alternator failure (although it does happen), but internal corrosion of the battery cables, as Thermo has indicated so many times. I have experienced this symptom on my 2002 X-Type, revealed by the overheating of one of the cable connections at the battery (see Thermo's instructions above). Cable replaced, battery light extinguished and 3 years later, still no problems.

 

Yes, Thermo is right but I had no choices to work with battery cables at the time when the bad luck happened. Besides there was NO possible way to open anything electric in the car with the car's battery completely DEAD. And nobody could. She simply played complete mute. I believe that both the alternator and the Walmart battery (now as meantime I did not have my previous battery anymore) had to be replaced. Unfortunately. If I had had the previous battery (taken by Walmart for $20) MAYBE that could have been charged with a new alternator. Or with a replaced cable. But she did not let me do it, as said, by her complete silence. Now I am curious (and not only me, thanks, Thermo) if her other voltage little headache (P0133) will stop lighting its own yellow hello too with this sacrificial change.

 

Thermo and you are right but I couldn't do any electric test with a completely dead battery (both batteries, my previous one and the Walmart little one were refused to be charged by both the previous (bad) alternator and the new alternator and the new alternator only proceeded to charge battery #3, an interstate R94 H7, an exact replica of car's original battery #1). Let's see now (thanks, Thermo) if this voltage renaissance will help with the other voltage little headache of my car, P0133. I hope it will.