Question about 2003 Jaguar S-Type

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2001 jag S type alternator check

What is the easiest way to check the output of the alternator?
I have my multimeter but the alternator seems rather hidden and hard to get to. my battery is dead and I want to check the alternator before i buy a battery, as it may be that my battery is good still.

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You probably have taken care of this by now (it is courteous to stop by and let us know that by commenting your message) but if you are in the US, most all of the chain parts stores will check it under load for you and surely tell you if either battery or alternator is ill. 

Posted on Nov 16, 2008

  • Steve Allison
    Steve Allison Nov 16, 2008

    Should have mentioned this in my previous comment; 

    For the future; you can check your alternator by measuring across the battery terminals with the engine running.
    Anything you find under ~13 volts is a bad sign. 
    Even at an idle and even if Jag still uses miserable Lucas electrical stuff, most systems will show 13.5-14.2 volts even at an idle and shouldn't rise above ~14.5 at higher RPMs.
    A voltage reading that is too high (>14.5 V) can mean one of two things: the regulator has failed or the battery is suffering from sulphation and approaching end-of-life. 
    The nominal voltage of a fully charged, healthy battery is pretty close to 12.67 volts, spec'ed at 12.6 (2.2 volts per cell).  



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