Battery Voltage too high

[nrandlexj40]

I have an issue with my 2010 XF 3.0 V6 Diesel

It has just thrown a number of faults - firing off various warning messages.

I plugged in the code reader and most of the faults seem to be voltage related.
I know these cars are very sensitive to weak batteries so I have swapped the battery for a new fully charged one that I already had and cleared the codes.
When I check the voltage across the battery with the engine running you can see the charging voltage increasing gradually and constantly.
It seems to be excessively high and after 10 seconds reaches 17.25v

At this point warning messages and beeps fire off on the dashboard and the central display goes blank.

The codes that keep re-occurring are:

PCM: P0659 actuator supply voltage A - circuit high
TCM: P0563 System voltage high
ABS: U3006 Control unit input power A
ICCM: U3003 battery voltage
DSM: U3003 battery voltage

I'm guessing that this points to an issue with the regulator - am I right that the regulator is part of the alternator - a new OEM alternator was fitted 18 months ago

Can anyone offer advice on what may be the issue?

Thanks

[BrianG]

Are you are sure your 'new' battery does not have a high internal resistance cell - a good test: does it crank the engine without hesitation with all the headlights on? If you are sure the new battery is OK then it definitely seems like a fault with the alternator regulator. The voltage should normally not exceed a maximum of 14.5V on a good battery. At 17.25V not only are you frying your battery but risking frying parts of the electronics too.

[nrandlexj40]

Hi Brian

The battery is good and cranked over fine - had the RAC look at it and they feel the issue is with the BMS unit giving false readings to the ECM.
I've managed to get hold of a good S/H BMS unit so will swap this out to see if that cures the problem.....

Fingers crossed

[BrianG]

Normally the regulator is internal to the alternator, so unless the BMS controls the alternator charging externally on the XF I don't think changing it will make any difference. If you measured 17.25 V at the battery terminals then this is a real voltage that is too high and not just an erroneous reading from the the BMS to the ECM.

[nrandlexj40]

Turns out it was a faulty alternator - not very impressed that a £500 Lucas alternator only lasted 18 months (of course the warranty period is 12 months)
Let's see how long this unit lasts

[BrianG]

Glad you fixed it. I didn't think Jaguar used Lucas parts in recent years, but it seems their quality hasn't improved much. Don't forget the original soubriquet from drivers and motorcyclists back in the day: "Lucas - Prince of Darkness"

[andypryce]

That’s not good. Was it another £500 to shell out? I think that’s worth pursuing with Lucas.

[nrandlexj40]

Yes - it was another £500 for the alternator - needless to say I will be making my feelings clear to Lucas (for what good it may do)

I'm just pleased that it doesn't seem to have 'fried' any of the electronics in the car

[andypryce]

Indeed, I guess could have been a lot worse..

[nrandlexj40]

Quick update on this - I took this up with Lucas (who it turns out are now Borg Automotive) and after some discussion they confirmed that the warranty period is actually 2 years. I therefore went back to the Jag Specialist who had fitted the alternator (and told me it was a 12 month warranty), forwarding on the Borg/Lucas reply. After a little discussion they blamed their supplier for stating a 12 month warranty and refunded the cost of the second alternator.
Now - I'm not sure who was pulling a fast one here - charging for a new item when it should be covered on warranty - but needless to say I've lost faith in this particular 'Jag Specialist'

If anyone can recommend a good independent in the Derby / Notts area I'd be interested.