2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Bad Alt or batt?

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Old Nov 21, 2006 | 07:20 PM
  #1  
cmanns's Avatar
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From: The yay, California
Bad Alt or batt?

I dont have a light going on but my batt will suddenly go to 6 and it wont turn on....wont even llight the P light..or turn on the radio...but before I tryed to start it the radio was on and it was at 12.5ish

When I get the car on sometimes (I sometime need the help of our chargers Engine Start mode) it idle's almost at the needle start mark when I turn on the lights..if I push the gas so it goes to about 2kRPM everylight gets brighter x[ so is it the batt or the alt?

Also whats a good batt to get?
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Old Nov 21, 2006 | 07:29 PM
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optima makes a good battery. you need to test your battery and test the output voltage at the alternator when the engine is running. sounds more like an alternator problem.... it probably wouldnt hurt to pull the alternator off and have it tested as well.
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Old Nov 21, 2006 | 07:58 PM
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Smoke moar
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From: The yay, California
I cant get them tested, the batt dies over night though or over 2 days...Ive had it on the charger for along time too.....

when its ideling and I turn on the lights the alt makes a wheerling sound and the idle goes down alittle like when you turn on teh ac...
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Old Nov 21, 2006 | 08:04 PM
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Take the batt to a parts store and have them test it. If its bad then its the battery, if its not you have a drain on your system more than likely.
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Old Nov 22, 2006 | 07:25 AM
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You can check the alternator yourself.

FSM tests – correct way

DMM tests – quick/easy (Sureshot)
Engine running, headlights & heater fan on high:
Alternator post to alternator frame = 13.5-14 volts steady (verifies the alternator output)
Alternator post to battery (+) = 0 volts (verifies the primary + wire)
Alternator frame to battery (-) = 0 volts (verifies the primary ground)
Turn off the motor, but leave the lights on.
Battery (+) to battery (-) = ~12.5 volts and holds steady. (verifies battery)
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Old Nov 22, 2006 | 07:59 AM
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perfect small write up My5ABaby!
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Old Nov 22, 2006 | 08:03 AM
  #7  
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Originally Posted by My5ABaby
You can check the alternator yourself.

FSM tests – correct way

DMM tests – quick/easy (Sureshot)
Engine running, headlights & heater fan on high:
Alternator post to alternator frame = 13.5-14 volts steady (verifies the alternator output)
Alternator post to battery (+) = 0 volts (verifies the primary + wire)
Alternator frame to battery (-) = 0 volts (verifies the primary ground)
Turn off the motor, but leave the lights on.
Battery (+) to battery (-) = ~12.5 volts and holds steady. (verifies battery)

Very nice very nice.

Are DMM also OHM meters, or there two seperate things. I think i seen testers that you can measure volts and ohms.

Jason NYC
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Old Nov 22, 2006 | 09:13 AM
  #8  
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Smoke moar
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From: The yay, California
The reason I think its batt is

I leave it on charger over night on both 10amp and 2amp modes, what happens is I can start it, we dont drive it btw....but I can start it like tha hole day after I charge it, less then 2 days later, turn key, says alittle more then 12 then snaps to the lowest it can go right when the engine trys to turn..

Even if I unplug it, it still F's up like that
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Old Nov 22, 2006 | 09:23 AM
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Originally Posted by ROTARYROCKET7
Very nice very nice.

Are DMM also OHM meters, or there two seperate things. I think i seen testers that you can measure volts and ohms.

Jason NYC
Yes, unless you have a really sucky one (never seen one that bad).

The one I have measures:
AC V
DC V
Ohms
Amps
and a couple others (resistors or something... stuff I don't use)

It's a pretty basic one from Radio Shack. $20 or something.

http://www.radioshack.com/product/in...rt&tab=summary

I think that's it.
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Old Nov 22, 2006 | 09:26 AM
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Originally Posted by My5ABaby
Yes, unless you have a really sucky one (never seen one that bad).

The one I have measures:
AC
DC
Ohms
Amps
and a couple others (resistors or something... stuff I don't use)

It's a pretty basic one from Radio Shack. $20 or something.

http://www.radioshack.com/product/in...rt&tab=summary



I think that's it.
very nice, ima order 1 thru my job
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Old Nov 22, 2006 | 09:27 AM
  #11  
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Originally Posted by ROTARYROCKET7
very nice, ima order 1 thru my job
Come to think of it, the one I linked broke. Which doesn't surprise me ($20...). I could also never get the leads back into the case because, well, it was basically impossible to cram them in there.

My analog one, which is the same thing basically except the display uses a needle placed over a scale (of sorts) still works fine. It's better for testing the TPS too because you can see dead spots much easier than with a digital one.

This isn't mine, but it gives you the idea:

http://www.radioshack.com/product/in...entPage=search

Somebody like Icemark could probably recommend a good one for a decent price.
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