Hi All,
I bought a 2010 jaquar xf 5.0 with 33k miles on it. I love this car.
It looks good and the drive is great! well yesterday after stopping at the gas station and filling up. my car just died. I had it boosted off and I was on my. of course Jag is closed so I go to the local parts store and they test the battery. It showed good and the parts guy suggested driving it to charge the battery. well after leaving the mall and heading home it dies again and I can't crank it. 1. the lights still come one inside and the headlights as well.2. should I wait and have Jag check it or replace the battery ay my local parts store. I'm so upset right now...

 

msinglj, our cars tend to be very picky about having a fully charged battery with full capacity. The first check that I would do is to see if the alternator is functioning. This is simple as you can take a multimeter and connect it across the battery. With the engine off, you should be getting 12.6 VDC (any less and that would indicate that your battery is not at full charge and should be placed on a charger before going any further). Once you start the car, ensure all electrics are off that you can turn off, you should see the voltage jump up to around 14 VDC and then coast down a little bit to 13.7 range (anything above 13.5 is good unless it is up in the 15V range). If you are getting less than 13.5 VDC, you have an issue with the alternator. With a good voltage here, turn on a lot of the electrics and see if the voltage remains pretty much constant (should not see it move more than 0.2V from what you originally saw). If you see a significant drop in the voltage, then again, this is pointing to an alternator issue.

At this point, turn off the engine and all electrics. Now place the car in a condition that the headlights can be turned on with the engine off. You should see the battery voltage at 12.5 V (or 0.1 V less than it was initially before starting the engine). If you see a 0.2 or more drop, then this is a sign that your battery is loosing its storage capacity. The final check is to watch the multimeter as you start the car. When you start the car, you should see the multimeter go from 12.6V, drop to the neighborhood of 11.0-11.5V, then do the jump up to 14V as the motor catches, then settle out at about 13.7. If on the dip the voltage on goes to say 12.0V or higher, then you have either a starter issue or a battery cable issue. If you see the battery drop to less than 11.0V, then you have a battery that is starting to go and it is dropping the voltage too much to allow the car to start.

Hopefully this will get you going down the right path to getting your kitty working again like it should.

 

I had a car a few years ago that did a similar thing.. would start at one point, then not at another point, the headlights seemed ok, although perhaps dull.. don't remember.. anyway, it turned out to be a dead cell in the battery or a short in the battery that cropped up now and again.
Also, a friend of mine had his car do the intermittent start and it turned out the starter motor had a dead spot and once rebuilt, it was all fine.
Not sure if any of these examples could be the issue.
Lawrence

 

You said heading home it died.

Did it die while you were driving it, or did you stop somewhere?

 

My car would do the samething. It would start fine, I would drive around town, then stop and turn it off. When I come back sometimes it didn't want to start, sometimes it would start no problem. I went to autozone and had the battery tested and they told me the samething. I can tell you right now I did change the battery after the third time the car wouldn't start for me and have not seen the problem again. I would buy a new battery before buying a starter or altenator, it will save you time and money.