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Recurring Alternator Failures

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Hi folks,

I own a 2007 IS250 sport which I've had since September last year. Car has been meticulously owned by the 2 previous owners and also by myself in my ownership. I was told by the previous owner when I bought the car that there had been some maintenance carried beforehand including an alternator replacement. Car has been faultless up until February when the alternator began to fail. I replaced it with a new/reconditioned unit from a reputable company through my trusted local motor factors. The old alternator I removed was a brand I'd never heard of so put the premature failure down to that.

Today my alternator died again. I inspected the wiring when I replaced it in February and again today and nothing appears out of sorts. I'm starting to suspect there is an underlying issue here. Has anybody had a similar experience with alternator failures in their IS250 or am I just so unlucky as to get another dud alternator the last time? There's nothing to indicate there's electrical problems with the car. It's not been modified, everything appears in good condition, Battery looks relatively new and holds charge there's never any issue starting after the car has been sat up.

Any insight or advice from people whove had similar issues would be much appreciated. 



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Check the Kw or ampere capacity of the replaced generators against the original. If lower, this may be the cause pf failure.

Check for a possible short circuit in the wires from the generator to their final destination. You will need a circuit diagram to do that.


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I know it’s prob not what you wanna here but I would put nothing less than a Denso on. Not cheap but if you have to revisit the problem then it very well may work out cheaper.

have you read this thread, and the problem James250 had with a replacement Alternator until he fitted genuine Denso?


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Thanks Texas thats great info. I typically do go for OEM parts, all my services I use OEM parts and did price a Denso but given the cost difference I opted for a remanufacture unit. Now though in hindsight I'd rather have forked out for a Denso. If it's known that spurious/reconditioned alternators don't agree with the car I'm happy to pay for a genuine one. Once it's not an issue with the car causing the alternators to blow as at the minute I feel like I can't trust the car. 

Thanks for forwarding on that thread link. Nice to know someone has had a similar experience and resolved it.

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Also check the Battery condition, it may appear OK and start the car fine but an internal fault can take out the alternator.

Also ensure the main earth cables from the Battery to body and engine are fitted and secured as poor earthing can cause its demise.

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