Just got my 05 VandenPlas out of the shop with major work. Discovered Alternator not charging battery. No red battery warning light! Voltsage neater shows battery slowly discharging as engine runs. Are there any connections/ fuses I can check besides battery cables and alternator connections?

 

nail24fac, I have diagrams up to 2003.5 MY, but not the 2005, but things should be fairly close for this system. Looking, you have 3 possibilities with wiring. You have the plug coming from the ECU to regulate the voltage. I think we can rule out the ECU being the problem as the car runs, so this would really only leave the plug on the alternator as a problem. The next potential is the power wire coming off the back of the alternator that feeds power to the entire car. This wire runs from the alternator to the starter, then on to the rest of the car. Since you are able to start the car, this limits where a wire may have been left off (either at the starter or at the alternator). Finally, you have fuse F35 in the passenger compartment fuse box. This powers the alternator field. If this fuse blows, the alternator will not output any power, but this would also affect the ECU and TCU of the car, leading to driving issues.

With all this being said, I would start with checking fuse F35 as this is the easiest check. I would next go after the starter as this would be the most likely location based on indications (car starts, no alternator light, but battery not maintaining charge). Finally, you are having to check all the connections on the alternator.

If you are still having issues, let me know and we can go from there.

 

Since the battery warning light is not on, the most likely is the main power wire off the alternator, as stated above. If we assume there is not a module failure your ECU is seeing that the alternator is putting out what it should. So the field is probably OK. It does not look at the connection to the car to verify the battery is being charged, just the voltage directly being put out by the alternator.

 

Yesterday I put the front wheels up on ramp. Checked Alt connections with bore scope. All appeared to be connected. Wiggled connection at starter. Started engine and the alt showed 12.4 volts charging. ???? The alt does have loud bearing noise, however.

Jag service dept says I need the $1300 alternator because others will not work. Has anyone put an aftermarket alternator that costs much less on there XJ8 with success?

 

Any alternator shop will rebuild it for a couple hundred bucks.

 

Bearings and brushes don't cost much, & are not difficult to install.

 

If it is only putting out 12.4v diodes/regulator needs testing.

 

I dropped in a low mileage used alternator when I had my engine bay apart. You can find them on car-part.com for not much money. Labor wise the job is a bit awkward in that I believe the passenger motor mount needs to be removed for room but there are how to's and videos out there. Now, while my junkyard alternator is working perfectly, my used power steering pump is not...

 

Diodes are available preassembled, on a metal plate, ready to install.
Requires some soldering, so you may want to have it done,
The recycled junkyard parts, are also an attractive, & inexpensive alternative to new.
Always throw a new set of brushes into those type of parts myself.
Cheap way to insure a better chance, of a longer lifespan, i m h o

 

Hi nail24fac,

Any good shop and most auto parts stores have analyzers that can test the alternator output for voltage, excessive AC ripple, and a failed diode.

I have used various remanufactured alternators from Rock Auto and Parts Geek on X350s. I prefer the OEM Densos, but they aren't always available.

As scooterforever mentioned, replacing the alternator requires supporting the engine and removing the right side motor mount and bracket. The first time you do it you'll think it's very difficult, but it's more fiddly and frustrating than difficult. A long 3/8" drive extension and flex/universal joint help a lot.

At the link below you can download the wiring diagrams for your car:

Jaguar X350 Electrical Guide 2005

Cheers,

Don