Purchased a '07 last year. About 75000 miles. The car died while driving and tech diagnosed a faulty alternator. The battery light came on immediately prior to the car dying. The alternator was replaced and seems to be working fine, however, now the battery light comes on when (I believe), it shouldn't. When I start the engine, the battery light may come on or it may not. If it comes on, it stays on until the engine is shut off again. If it stays off when the engine starts it stays off. I had the battery checked and the tech said that it was fully charged which makes me think it is a faulty sensor, component or gauge.

Yesterday, something different happened. While idling at a red light, the engine gave a cough or hiccup and the light came on.

Has anyone experienced anything similar? I'm looking for suggestions or tips to diagnose and correct the problem.
Brian Walker

 

It sounds like you either have corroded, loose or bad cable connections on the battery. The cables are known for corrosion internally.
Remove and clean the battery cable clamps and posts. Check the cable for stiff brittle "feel". You might also want to clean the other ends of the cables.

When the vehicle is started the battery voltage drops. The alternator is signaled to provide a higher charge rate to bring it back up quickly. The alternator then settles out at normal output. I suspect the charge isn't getting back to the battery due to the connections/cables and that is why you see the light.

 

Thanks for the tip. I believe that the dealer claimed that the cables had been replaced as part of their pre-sale inspection (I'll have to check documentation on that point). I'll check the connections at both ends of the cable though to make sure that they are tight. I appreciate the advice. I'll follow up.

 

Have you taken it back to the place that replaced the alternator? Obviously they did not fix the issue. I'm not saying the alternator did not need to be changed, but generally they are pretty robust and these sorts of issues are usually traced to something else.

 

Actually, I did take it back. The battery light came on as I was driving it home from the shop after the alternator had just been replaced. I immediately called the tech and he thought that it must be a faulty replacement alternator so he ordered another one. I put the battery on the charger when I got home and the problem changed (to the one I described). I took the car back to the shop and they did the battery test and determined that it was fully charged and that the alternator seemed to be working fine. They returned the new (refurbished) alternator that they had just ordered. I have it booked in for followup testing but I was hoping someone in the forum knows the source of the problem and the solution. The tech was stumped and I'd like to avoid lengthy and costly diagnosis if possible. I appreciate the suggestion.

 

On an S-Type, which has a similar charging system I think, it would be due to an incompatible alternator.

 

Are there/were there multiple types of alternators available for different years, different engine sizes etc? If there were different types available, I could see how something like this could happen but if there was only one alternator-type available for this model for 2007, I'm not sure how the wrong alternator would go undetected. I'll have to refer this suggestion back to the tech when he is doing his diagnostics. Thanks for the tip.

 

Typically a replacement is a cheap aftermarket one.

Or it could be hooked up wrongly.

This is not rocket science for a COMPETENT tech to figure out.

 

If you had them install a "refurbished" alternator, that could be the problem.

 

I checked out new OEM and the price difference could not be justified. As you say, it could be a bum replacement. I'll pass that along. Thanks

 

Point taken. Thanks again

 

same thing happen to my Ford Focus, after replace the alternator,I start the engine, no light come on, but I drive the car just about one minute the battery light come on, the technician couldn't find the short or the problem, if I don't drive the car few day the battery still not drained.