Hi I have a 2004XJR 4.2 supercharged its done 105K and has recently been discharging the battery I have seen threads that suggest the voltage regulator can be the problem and that to prove this on the earlier 1997/2003 models I need to disconnect the negative lead from the regulator. is there a fuse that can be taken out to prove the fault. is there anything else I can try? I have seen loads of threads for the earlier model Can anyone help please

 

The charging system is controlled by pulse width modulation from the ECM. What battery is in the vehicle now? What is it's age? Have you had it tested?

Also understand there is a lot of complexity with various systems that will continue to draw current on these vehicles, up to hours after the you have exited the vehicle. It can be as much as 5+ amps for minutes, to up to an amp or more 40+ minutes afterwards. Every time the SCP network is called, it will reset these values and restart the clock. It should have a proper quiescent current draw test performed.

 

Hi David thanks for your reply The battery is new and at stanby has a terminal voltage of 12.82 Volts.
When charging at tickover it is charging at 14.83 Volts.
I have been disconnecting the battery while its at home in my garage. Just checked the current drain after it has stood without the battery connected for 7 days and its drawing 2.25 Amps

 

You have a serious drain on that battery. Disconnect the alternator and see if it drops.

I would also check the flap in the ignition barrel is closing when you remove the key.

Does your alarm chirp work, if not then this is another possible drain.

Switch off all auto functions and check all interior lights are going off.

 

Thanks jimbov8 Can the alternator be disabled totally with removal of fuses or is the regulator always live

 

Hang on a minute, I'll get back to you.

 

Pull fuse F33 5A in the passenger junction fuse box. That circuit is only live when the ignition is at position II so if you think it's the alternator then it would be better to disconnect it.

 

Jim, I appreciate your input, but quiescent current draw is complex, and can easily put 5+ amps for minutes after SCP network activity. Opening a door or call for PATS or a myriad of other things call the SCP bus. There are specific tests Jaguar has published in diagnosing quiescent draw. Not following these tests will lead users to replacing modules and devices that are not in fact faulty. There are no voltage regulators in the alternator in the X350, as was in the X308, and all charging regulation is controlled by the ECM.

 

I wasn't referring to quiescent draw, my observations are to do with a parasitic drain and nothing else.
I'm well aware of how the quiescent draw affects the readings one may see when the car is shutting down but thanks for bringing it up.

 

Sadly, you can't separate the two.

 

Well perhaps you don't know as much as you think you do so therefore I'll wait while Mike gets back.

 

I've got 40 years in the industry, and an ASE Certified Master Tech. Worked for one of the Big 3 for over a decade. Are you factory trained or Jaguar certified? (also, on X350, there is no flap on the ignition barrel, the Tibbe key pushes directly against the tumbler on insertion)

From a diagnostics perspective, they cannot be separated, since both affect current draw.

 

When you reconnect the battery, it will awake the SCP network. What you will have to do is remove the boot lamp, and leave the boot open. When you reconnect the battery, walk away for one hour, and upon return don't open a door, or use the fob, and check it. I would like to know what the draw is at that time. Leave the vehicle PATS unarmed. There are a number of active relays and circuits in use at reconnect.

 

I really appreciate your responses and will try David's latter suggestion and get back with the reply thanks again Mike

 

Hi David sorry for the long delay it looks like I have an intermittent problem since receiving the advice I have carried Quiescent current tests many times some with the alarm set and some without. After about 45 minutes to an hour with the alarm set the drain is about 22Ma and without the alarm set it is about 36 mA.
I never used to alarm the car while it was locked in my garage, but have done since carrying out these tests. I am stumped but concerned that the problem will return and leave me with a flat battery without any warning. Thanks though for the advice.