Hello from the Midwest! My wife's 2003 XJ8 has been a fairly problem free car. This past sunday the Alternator (factory unit) began screaming, not like a bearing but like it was working it's guts out. Then it stopped charging and I barely got home. By the time I did, the turn signals started flashing quickly and the transmission went into 'limp in' mode, 2nd gear only. There were no telltales on the dash that anything was wrong.

I removed the alternator and have it tested, it spun up fine but made the same scream when electricity was applied and it then tested bad in all areas. I installed a rebuilt alternator which was identical in appearance. All seemed well, but the dash now illuminates the battery telltale and the display says 'Battery not Charging'.

I have 14 volts at the back of the alternator at the battery stud. There is 13.6 volts at the battery and at every Power Distribution panel in between. All fuses (especially #2 under the bonnet) are good. I also checked the connection of the Engine Ground Strap at the rear of the engine on the passenger side of the car, no issues. I checked the False Bulkhead Connector and all is clean and tight there also. I did a hard reset, this solved nothing. I decided to take my meter and jump pack with me and drive the car. The car operates as normal except for the dash messages. I drove with headlights, road lights, and a/c on maximum with no problem. I drove the car to work the next day again without issue. Now my wife is back to driving it, but I need to rectify this telltale situation.

I have come up with one question (other than why isn't it fixed), near there battery in the boot, there is a long wire with a female spade connector on it. Wire is White/blue. It is connected to nothing. I do not know where it belongs, if it for some option this car isn't equipped with, or if it just is supposed to dangle there??? Anyone experience anything like this before. The car says it isn't charging but I know it is. Any assistance will be greatly appreciated. I have 19 years as an auto technician and it seems I need a little more! LOL.

Thanks for your time and reading my lengthy post.

 

There was a thread with the same problem recently, do a search for not charging and you will probably find it. I assume the battery was disconnected when you replaced it.

The wire in the trunk was used when the car was being shipped and can be ignored.

 

The wire in the trunk was for a transport module which was removed at the Dealers and returned to Jaguar for the next batch, a real do nothing wire.

In some cases the error codes will need 20 cycles (ignition and drive) for those to go but they're generally not flashed warnings? I'm not sure but there have been issues with the neg lead in the trunk, maybe check and flood the ends with solder.

Keep the battery pack handy and see if it goes out!

 

Why the drop from 14V to 13.6V?

What do you have at the terminal stud at the false bulkhead:

a) when VDM lead grounded to alternator case
b) when VDM lead grounded to something else

Don't forget, the ground circuit is also part of the power circuit.
You might need to clean the mating surfaces of the alternator forming
its part of the ground circuit including the alternator bracket to engine
interface. I shined it up and applied conductive grease which can be
had from Home Depot for about $4/tube in the electrical section.
Meant for aluminum wiring connections and required by code.

And ...

on that particular model of alternator, the regulator is an internal sense.

IT DOES NOT KNOW THE VOLTAGE OUTSIDE OF THE ALTERNATOR CASE

The charge light is the only thing the lead from the regulator controls.

Lots of rebuilts use the wrong regulator.

Or perhaps the wire/plug got mangled in the operation. The plug is
sometimes a bit stubborn to remove. Silicone grease on the outside
of the plug shell is helpful in inserting it correctly.

Speaking of rebuilts, a self rebuild can be much better than a bought
rebuild. Especially if you can keep the original regulator. Everything
else is generic.

And ...
does the alternator come up right away at start? otherwise the field
wire might be suspect and it is in self exciting mode.

++

 

The charge sense wire that Plums is referring to is the yellow wire connecting to the internal regulator built in to the alternator. As he said, other folks have reported getting multiple replacement units from the same vendor that have your exact symptoms apparently stemming from use of the wrong regulator in the rebuild.