My Jaguar has been very good to me (relatively speaking). 1999 XK8 convertible, bought it 3 years ago with 96k miles, just passed 120k miles.


I've wrecked it, and fixed it, had the typical error messages:
*ABS failure - No affect to drivability
*Stability control failure - no affect to drivability
*Transmission fault - Went away after restart, smooth as silk before and after
*Steering column stuff - I just deal with it
*Windows stuff - Simple reset
*Dreaded green shower -ew!


And now as of yesterday, the Engine Fail safe Mode. Went away after restart, smooth *** silk before and after.




After reading everything on this forum, I'm not gonna panic. I'm just going to buy a new battery.

 

Probably a good move. Having it load tested may reinforce your decision, but if it's getting old I agree with just replace it.

 

Great gobs of detail in your post of problems . . . except the only fact that matters . . . your "standing battery voltage" . . . ie the voltage measured at the battery terminals next morning after any recharge. High 12s is great. Anything below 12.6V is asking for trouble - typically enough to start car but not enough to run electronics. Any 11s spell a dead battery that no defibrillator can ever resurrect. Buying a new smart charger or battery tender will maximize your new battery's life and reliability.

Cheers,

Ken

 

My experience says batteries last "about" 5 years. I bought this car 3 1/2 years ago from a car lot so I know the battery wasn't new. If the battery was two years old when I bought it, then it's potentially six months, or more past due for replacement.

 

If you do not intend to part with your XK8 in the forseeable future , putting in a new 100Ah new battery now is a no-brainer...

Cheers!

 

Honestly, it is best to go with numbers. Check the battery after it has been sitting a while (like overnight). You should have well over 12V at rest. You can measure with a Voltmeter at the battery, or even with a cheap ELM327 device at the diagnostics connector.

What really matters is to have good voltage as the engine cranks. If low, the electronic modules get confused and results in nothing good. You can also have a local parts store do a (free) load test to confirm that part.

There is probably a sticker of some sort on the battery itself to tell you the manufacture date. Separately, check the type of battery. AGM batteries are referred to as "maintenance free", but most others have weasel words like "low maintenance", meaning you have to maintain it. The top cap has to be popped/pried open, and the cells topped-off with distilled water. You might gain a fraction of a Volt by doing just that, and delay the purchase of a new battery for a while. We all know batteries will fail eventually, but this one is already paid for, why not use it to the end? A battery is loaded with sulfuric acid, so only open the top of you have read and understand what the manufacturer tells you about it.

Best of luck, keep us posted.