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i hate wierd electricla problems


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7 replies to this topic

#1 nipper

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Posted 07 November 2006 - 09:46 AM

New altenator, walmart battery (came with the car ) from 2005.
Battery at 13 volts in the morning (fully charged),
Battery load test passes in the morning.
Start after 4 hours or more, car voltage is 11.9 -12 volts for 3-4 minutes, then jumps to 14 volts.
Under 4 hours output is 14 volts
Over 4 hours (est) low voltage scenario.

any ideas?
i am thinking a lazy alt.

nipper

#2 Wayne Boncyk

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Posted 07 November 2006 - 10:50 AM

New altenator, walmart battery (came with the car ) from 2005.
Battery at 13 volts in the morning (fully charged),
Battery load test passes in the morning.
Start after 4 hours or more, car voltage is 11.9 -12 volts for 3-4 minutes, then jumps to 14 volts.
Under 4 hours output is 14 volts
Over 4 hours (est) low voltage scenario.

any ideas?
i am thinking a lazy alt.

nipper


Sounds to me like you've pegged it. I'd suspect alt diodes, and with these Sube alternators you're gonna have to swap out the whole thing. You're seeing exactly the same symptoms that I saw on my original alternator ('96 OBW), and Subaru actually issued a recall on them back then. Do you truly have new, or a "remanufactured" replacement unit? Wonder if you ended up with one of the gimpy original OEM alts when you swapped it out last time...?

#3 Cougar

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Posted 07 November 2006 - 11:51 AM

The problem most likely is with the alternator Nipper but I would check the connections to the alternator to make sure that things are ok there. You should see voltage readings close to the battery voltage at all the connections. If it is lower then you need to check that lead for a problem.

From your post it sounds like you are saying that the battery voltage is low after the car is setting for a few hours which may mean there is a drain on the system. If that is so and there was no problem like that before the new alternator was installed then it would seem that the alternator is backfeeding a current and needs to be replaced.

#4 nipper

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Posted 07 November 2006 - 11:55 AM

The problem most likely is with the alternator Nipper but I would check the connections to the alternator to make sure that things are ok there. You should see voltage readings close to the battery voltage at all the connections. If it is lower then you need to check that lead for a problem.

From your post it sounds like you are saying that the battery voltage is low after the car is setting for a few hours which may mean there is a drain on the system. If that is so and there was no problem like that before the new alternator was installed then it would seem that the alternator is backfeeding a current and needs to be replaced.


actually the battery voltage is fine. This happens only after a restart after 4 hours or more, then it drops down 12 volts. I checked the voltage before starting and it was 13.5 ish, after the start from sitting overnight it was 11.9ish

nipper

#5 nipper

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Posted 07 November 2006 - 12:00 PM

Now would this be a fault of the regulator or of the diodes? I would think regulator.

nipper

#6 Wayne Boncyk

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Posted 07 November 2006 - 06:24 PM

Tough call without being able to do some load testing, nipper. But whatever is causing the problem, you will want to get it taken care of before too long, or your battery will soon be toast. Any time spent at less than around 12.5 volts (average of 2.1V per cell) means that the electrodes are sulphating, and pretty soon you won't have enough electrolyte left to hold any charge.

#7 Snowman

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Posted 07 November 2006 - 06:49 PM

One thing I've found that probably isn't related but you never know, is that the main power wires going from the alternator to the power distribution box degrade over time on these cars, often resulting in a voltage drop of .5v or more. Like I said, I doubt that's the issue in this case, but I'd check just to make sure.

#8 Cougar

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Posted 07 November 2006 - 09:32 PM

It could be the regulator Nipper. The trouble may also be with the field so check the voltage on the small wires going to the alternator. Be sure that they are near the battery voltage. If the field doesn't energize the stator windings then you have no output.




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