My wife's 5.0 XF died yesterday. I took out the battery and replaced it with a new one. Off she went. today it died again, this time throwing up a battery symbol and a warning triangle. She also mentioned it throwing gearbox fault messages at her. I checked the battery voltage and it was under 11 volts. Battery is now on charge so - hopefully - like yesterday a fully charged battery will get it going. In the "old days", I would assume it's the alternator and replace it, but with these complicated modern vehicles I wonder if it's something other than the alternator. Car has low miles - maybe 40k miles max, but it is obviously 9 years old now.

I assume in the absence of JAg diagnostic gear (I do have a CAN OBD scanner but nothing more advanced) the cheapest route is to just buy and install a new alternator and see what happens?
Is access really difficult?

Thanks guys.


p.s. Charged the battery for a while, and put it back in the car and got the car home which is a relief as it was badly parked on a side street.
Got to be the alternator OR the wiring from alternator to battery, we do have rats around here which will chew on damn near anything.

 

"I assume in the absence of JAg diagnostic gear (I do have a CAN OBD scanner but nothing more advanced) the cheapest route is to just buy and install a new alternator and see what happens"?


You've already replaced a battery that may or may not have needed replacing. Now you want to buy and install a new alternator to see what happens? JMHO, but if it were me I would take the car to an auto electrician and have them diagnose the problem. They can tell you if you need a new alternator. Wouldn't you feel silly if it's just something like a loose or broken wire? It's your money and your car. If you want to keep guessing and throwing money at the problem then go ahead.

 

Thanks Stu,
Well, I did take the battery back to the store I bought it from for a diagnosis as it was only two years old and they - obviously wrongly - diagnosed it as bad and gave me a new one under warranty so it didn't actually cost me anything. There aren't many things that can affect the battery, either the battery itself or the alternator, or the wiring. I am going to put the car up on my portable lift and check the wiring from alternator to battery, if that is good I am left with the alternator UNLESS there's some intermediate electronics that might be involved? To my knowledge though the voltage regulators are always internal to the alternator. I think the local store will check the alternator for me so I can and will do that before buying.

 

Okay, please keep us informed.

 

Hmmm, well I've figured out there's a 3/8" square hole in the bottom of the belt tensioner. BUT, how are you supposed to get out the third bolt on the top of the alternator? It's obscured by another pulley.

Helllllppppp!!!

 

Anyone? Surely someone has removed an alternator from a 5.0 XF?

The factory manual is useless. It shows a single drawing of an alternator with the three bolts in a highlight color - but no instructions on HOW to get to the top bolt around the pulley.

 

Hard to believe a guy on another thread here can get 42 responses on how to change out his battery which is almost like "How do I put gas in my car? , and yet no one has any idea how to remove the upper bolt when removing their alternator and navigate it around a pulley?

I've seen guys here rebuild their S/C motors, so an alternator swap should be like eating breakfast for them?

Oh well.....guess I am on my own.

 

I've never tried to remove the alternator so I don't speak from experience but Bigg Will did an upgrade to his that's documented in one of his posts. Also on the XJ forum there is a recent post about using the zip tie method to change out the tensioners. The OP has attached a couple of topix PDF files and the one covering the tensioner replacement shows how to remove the alternator. It looks like a couple of pulleys/brackets need to come off first to access the alternator. Take a look at that and see if it helps.

 

All it takes is a voltmeter to find out if the alternator is working.

 

Because disassembling half the car just to get to the part needing replacement is standard operating procedure on Jaguar and any given european import.

 

TXFIREBLADE: Thanks! I'll try to find those posts.

LOTUSPRITSE: A voltmeter on the battery will tell you the battery isn't being charged, it won't tell you if it's the alternator, the wiring or some ECM telling the voltmeter NOT to charge. I know the battery isn't charging, I now know the wiring hasn't been chewed by rats, so the alternator is the obvious next step to test. 9 times out of 10 it's one of the diodes in the rectifier. If the shop has an automated way to test it, I'll let them do it, otherwise I'll test the diodes in the **** end of the alternator individually.

LITTERED: Ain't that the truth. Wish I was working on one of my old Bel-Airs, Alternator stood there, right in front of you with a cubic foot of air space around it.....sigh......

 

Turns out the interfering pulley in question is an idler pulley, but looking at the belt routing it looks to be turning in the opposite direction to most of the other pulleys on the motor which makes me wonder if the retaining bolt is a left hand thread. I obviously need to know this before I try taking it off!

 

Dude, just check the voltage at the alternator. That's how you isolate the alternator.

 

Dude, I've already checked continuity of the charging cables and know it isn't charging the battery so what's the point?

Now, if you can tell me if the idler pulley just above the alternator is LH thread or RH thread that would be really useful?

 

This is interesting, and annoying.....seems like the BMS and an ECM somewhere via the LIN connection on the back of the alternator can dictate how and if the alternator delivers charge to the battery.


The BMS module measures battery voltage and current
which provides information about the battery state of
charge (SOC) and state of health (SOH). SOH measurements
provide an indication of battery condition. The
BMS compares this information to new and used stored
battery values.
Battery information is then communicated to the rear
junction box (RJB) over a LIN bus connection. The RJB
transmits the battery information to the instrument cluster
via the MS CAN bus.
The instrument cluster displays battery charge warning
messages to indicate generator or BMS faults. The
instrument cluster also acts as a gateway between the
MS CAN and HS CAN bus networks to transmit battery
condition information to the ECM from other modules
(audio and climate control, for example).
Based on the information received from the BMS module,
the ECM will control the output from the generator
via LIN bus. The ECM can also request the switching
off or reducing of power to electrical loads if necessary
and override the BMS signals if a fault is detected.
The BMS also monitors battery status with the engine
switched off, sending a signal to switch off the infotainment
system if necessary to protect the battery condition.
Once triggered, the engine must be run for at least 5 minutes
to charge the battery before the infotainment system
will be allowed to operate with the engine switched off
for a second time.
Periodically the BMS module will instigate a self-calibration
routine. To self-calibrate, the BMS first charges
the battery to its full condition.
Once the battery is fully charged, the BMS will discharge
the battery to approximately 75% of its full state
of charge, but never lower than 12.2 V. The time taken to
complete this part of the routine is dependent on the
electrical load on the vehicle and the length of time the
vehicle is used.
When the second part of the routine has been successfully
completed, the BMS will return the battery to its
optimum level of charge. The optimum level of charge
will be between 12.6 V and 15 V, depending on battery
condition, temperature and electrical loading. This process
is run approximately twice a year.

 

Ken,

Did you read the Topix instructions on removing the alternator I directed you to?. I didn't see any mention of a thread change for any of the parts.

 

Maybe one with a logging feature.

 

I don't care about your situation, I am just correcting bad info that you were putting out there for the world to see. It's a full time job for me.

 

Do you understand ohms law? Whether I check at the alternator or at the end of a cable that has proven continuity it's the same thing.

There's always a guy like you on every forum.

 

TX, no I didn't locate it at first search, but having re-read your post I see it's probably the zip tie post referring to the cam chain tensioners on the XJ forum.
Thought I'd read on the many posts I've searched that the belt tensioner is threaded LH and its pulley rotates in the same direction?

Thanks again.


Just checked those topix pdfs. Supposed to be for a 2011 NA XJ motor, yet a drawing or two on each pdf shows a second belt tensioner near the alternator which I thought was only on the S/C motor? Maybe the XJ and XF motors were configured differently? I know the Range Rover variant is. Time to go back under the car.....