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XC90 V8 starting issues - alternator? (but I want to be sure before dropping $grands)

Had our 2007 XC90 V8 for 18 months now, noticed starting was weak when we bought it but was told it had already had a new battery a few months earlier which seemed to be borne out by evidence provided. Starting remained sluggish but always did start for many months, and experimenting with jump starters or pulling battery out and fully charging it overnight seemed to provide much more enthusiastic turnover which lasted for a few days then dropped back to reluctant.

I took the battery to be tested and it came up with a clean bill of health (even from the battery store who obviously would prefer to sell me a new one) and I have tried swapping over with a battery from another car which has no issues - same result.

It has now let me down a few times - randomly seems to drop voltage down into the 11s and then not start, then after jumpstarting and driving 5 minutes home, test with multimeter and its up over 12.5. Have also tested with multimeter while car is running, randomly sometimes get 13.5v other times get between 12.2 and 12.6. Also extremely rarely get any error messages unless the battery has dropped right down low and then its a random grab bag of all kinds of stuff which goes away once charged up again.

I know alternator is a known issue with these models, and have no issue biting the bullet and replacing it - but Im wondering if there could be any other issues that could explain these symptoms, or any other tests or troubleshooting I could do to make myself more certain that the alternator is the issue?

Also if I go down the replacement route, anything else I should look at while its pulled apart given it sounds like its almost an engine out job? What about this cooling ducting to the alternator Ive read about?

Many thanks for your help and advice in advance!


  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    @iceton1975 you had same didn't you?
    Workshop had this issue?
  • have come across a few threads describing similar issues being solved by replacing the starter motor as well...
  • wondering if logging some parameters with DICE could be useful (I dont have one so would have to borrow/buy one) or can I test some other way eg multimeter, cheap ebay OBD?
  • http://forums.swedespeed.com/showthread.php?170139-Tutorial-XC90-V8-Replacing-the-alternator&amp=1

    It's not all that hard or that much effort
    Known good alt should be sub $400

    One thing to check is the battery cables as that would prevent effective charging
  • starter motor issues on these and have done plenty.
  • Just before we bought her, our S80 V8 had starter motor issues. Ronton's in Adelaide advised us it's a known common issue in V8s, as they should fire up very quickly when you hit the start button. They replaced the starter motor and it's working great now.
  • Mick at Rontons is a good operator we supply him plenty of parts, highly recommend if in south aus.
  • thanks all, appreciate the input. sounds like it could be either the alternator or the starter motor (or both I guess? - or something else like loose/damaged cabling)
    How would one go about narrowing down and diagnosing the actual issue so that the right thing can be replaced? Knowing my luck I will start with the wrong one and work my way through to the right one spending billions along the way
  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    Have it all tested by a good indie technician.
  • still havent pulled my finger out and taken any action but by way of update, have noticed sound like arcing electricity while driving - roughly 1 crack per second - anyone come across this before?
  • Like zapping from around the alternator area
  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    see above , quick...
  • Lubing up wallet....
  • Ok so I have a brand new alternator and a brand new cable from there to the starter. It had got so hot that it had melted/burned off several cm of insulation! I also have a brand new 900cca battery, and the car is starting and running much better. Still not quite as lively as others ive heard so probably a starter motor replacement on the cards sometime in the future too.

    Anyway, despite all that, still hearing zaps from the alternator area! Has been suggested possibly static from the belt? Have checked all earths (motor came out to swap the alternator)

    Any ideas? Next plan is to try and locate the exact source of arcing, need to get on a hoist in the dark

  • If the starter motor wiring had lost insulation then its possibly the same issue with the alternator feed from battery

  • Cheers mate, it was all checked while the motor was out, also had auto elec check out everything and tested for voltage drop and impedance etc

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