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Old 04-05-2009, 06:44 AM   #1
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Help Lil Bastard

I am what I think might be a minor problem but not sure...

Ok I replaced my alternator with a Bosch one since my alternator was trashed. I also recently bought a Optima Red Top battery R34 about two weeks ago. When I first installed the battery about a week or so later the car was idling in my driveway and just plain out died. So my friend tested the alternator and found it to be no good and that I was just running on the juice of the battery and it was not recharging. So after replacing the battery my friend got this idea to see if the alternator was running good so he put a tester on it and it came up basically alittle over 800 cold cranks. He also stated that my car should run off my alternator if he pulled off the positive cable of the battery terminal. So with that he did it and the car died instantly. Is that true that it is suppose to keep running?... Well after reconnecting the battery terminal I restarted the car only to find that my cluster looked like a christmas with all the lights on. The lights that are on : TC, Triangle with exclamation in the middle of ,Abs,and a picture of the battery.... I know for sure that the lights were not on before swapping out alternators but not sure if the lights were on before he disconnected the positive terminal while the car was running.
I then ran a Durametric software to see if there were any error codes. Nothing came up at all expect the passenger seatbelt buckle and that is because the seat has been removed from the car in order to do the alternator. The lights are still on after running the software. I then went to check out the battery voltage by putting on a battery maintainer which showed that the battery was half charged not sure why but it was... I have at this point have the maintainer connected to the battery to recharge it... Any ideas what the hell went on? I mean ..There is no codes on ecu but the cluster lights are on ?

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Old 04-05-2009, 07:39 AM   #2
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Although some say I am a bastard, I am not Lil Bastard. lol

It sounds like you have a bad alternator or loose wiring from the install. I'd pull the alternator out and bring it by a local Autozone and let them test it to find out for sure.
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Old 04-05-2009, 08:55 AM   #3
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Back in the day of cars without computers, you could have pulled the pos battery teminal to see if the alternator was working correctly. But that isn't the case with today's cars anymore.

The computers in the car require the clean signal that the battery provides for them to work correctly. The alternator simply recharges the battery, and can not safely run the computer control devices in the car.

If you are lucky, you friend another alternator.
If you are unlucky, you friend the computer.

I recommend against ever doing that again in a modern car.

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Old 04-05-2009, 09:49 AM   #4
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You are wise. A thread came up a couple of months ago and I tried to explain about the bucket (battery), pump (alternator) and the water (electrical power). And was basically told I was out of my mind. Everyone seams to think the battery is only used for starting the car and after that the alternator takes over.

I've always been taught that electrical power comes from the battery, the alternator supplies power to keep the battery fully charged. During high power demands (fuel pump, ECU, lights on, top coming down, radio on, heated seats on, etc) is why the battery is so big, it needs all that capacity to keep up with the demand.
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Old 04-05-2009, 10:37 AM   #5
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Check the battery with a DMM - car off, terminals removed. You should see 12.8-13.2 volts.

Replace terminals, start the car, run lights, radio, heater, and test again. You should see 13.5-14.5 volts - that's your alternator voltage - spec for the Bosch alternator.

There is no test for cold starting amps, I dunno what bs your friend was feeding you.

Cold starting amps is a theoretical number under certain conditions. It is used to sell batteries, not test them.

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Old 04-05-2009, 06:58 PM   #6
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I fixed the wires that were coming out the alternator that needed to be connected to the bolt and held on with a nut. Everything is OK now.. No need for a new alternator or battery Thanks for the advance Lil and others

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