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Old 09-16-2010, 05:43 PM   #1
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Default Alternator. How to check.

Hello.
I need to check my Alternator. I know it charges the Baterry, but i think it do not do it properly.
When i change the baterry it crank fine, but few days after it do not crank as well. I change the baterry because the cranking was awfull and when i need to crank the car with another batery it goes perfect.

I change the baterry and it goes perfect, but in 2 or 3 days, was the same.

The voltage with the car off is 12.2 and with the car running is 14.2
I think maybe the estabilized or the charging circuit is bad. Is posible i could check them easy?

The car is a mk1 1.6 JRSC@8 psi.

Thanks.
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Old 09-16-2010, 05:47 PM   #2
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Sure sounds like alternator. Also check to make sure you don't have any corrosion on the battery post connectors or at the alternator.

If you were in the U.S. I would advise you to go to Autozone (auto-parts store) to have them run a diagnostic on the alternator (which they can do with the alternator still on the car).

Do you have any similar stores in your part of the world?

Edit: After re-reading your post, it sounds like you might have a parasitic drain on your battery.
Use this method to check:
http://www.wikihow.com/Find-a-Parasitic-Battery-Drain
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Old 09-16-2010, 05:48 PM   #3
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Something in the car drains the battery. Remove the ground wire from the battery next time you park overnight, and next morning, reconnect it and see if it is ok.
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Old 09-16-2010, 06:48 PM   #4
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If when running the voltage is 14.2, the alternator sounds fine.

Ditto what Reverant said. Disconnect the battery when you leave the car for a long time.
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Old 09-16-2010, 06:57 PM   #5
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And you only need to disconnect one terminal
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