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Discussion Starter #1
So this morning when I wake up I go and disconnect my negative terminal to reset the ecu, 20 mins later I got connect it and the car starts up fine I drive for about 30 minutes everything is fine. About 2 hours later I try and start it and my gauges come on and then die. It seems like power is turning off/on. So I check all connections everything seems good. I test my battery with my mulitmeter 12.6 volts. Car still wont start, nothing. So I jump it and it starts right up. Now my battery light is on, I drive it a little and then I start to hear like a belt whining noise, so I limp it back to my house. (Thinking its the alternator).So I pop the hood and the noise it gone I try revving it up and its silent, the noise only happens when the car is in gear under load So I turn it off and all power is lost again. But my battery still has 12.6 volts.I jump it again and the battery light is off and I test the voltage at the battery when runnning it's 13.7. I pull out and the noise is still there bring it to my driveway pop the hood, rev it up no noise. Is this my battery or my alternator or both?? I dont know whats going on here, Its just one problem after the next. Someone help me out.
 

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If I was you, I would jack up the front end of the car and put it in gear. Then
try to find out where the noise is coming from.
As for you problem, I'd load test the battery. You may have good voltage when
checking it with a meter with no load. Check the voltage with the vehicle off
and you high beams on and see what it does. If it drops voltage fast you most
likely have a battery problem. If the voltage goes below 10 volts within a like
thirty seconds I'd definitly replace the battery. If your getting 13.7 volts with
the vehicle running your alternator should be fine unless you find out that it
is making your wining noise. I hope this help you out, or at least gives you
a place to start.
 

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Are the cable connections ok? Your talking about power, then no power, start then no-start, etc.- sounds like a bad connection somewhere. If the batt light is on, it's probably not charging, then if it suddenly starts charging, you may well hear some belt noise, b/c the alternator is sucking up some hp. Remember that when the alternator has an electrical load placed on it, it becomes quite stiff to turn- it doesn't always just freewheel like it does on the bench. So that could be your belt noise. I suspect the battery connections because jump-starting seems to work for you. Maybe the jumper cable clamps disturb the offending connection just enough to make it work for a little while.

You make it sound like you reset your ecu every morning. Is that so? Why is that?
 

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Discussion Starter #4
Blurvfocus said:
Are the cable connections ok? Your talking about power, then no power, start then no-start, etc.- sounds like a bad connection somewhere. If the batt light is on, it's probably not charging, then if it suddenly starts charging, you may well hear some belt noise, b/c the alternator is sucking up some hp. Remember that when the alternator has an electrical load placed on it, it becomes quite stiff to turn- it doesn't always just freewheel like it does on the bench. So that could be your belt noise. I suspect the battery connections because jump-starting seems to work for you. Maybe the jumper cable clamps disturb the offending connection just enough to make it work for a little while.

You make it sound like you reset your ecu every morning. Is that so? Why is that?
I reset my ecu this morning because I had a vac leak through my boost gauge that I didnt know about so I reset it so it would re learn the parameters with the leak fixed.

Why would the alternator only make noise in gear? and not when revving in neutral.

I jumped it again then disconnected the negative terminal on the battery and the car died. Doesn't this confirm alternator?I also have a jrsc so its hard to get to the wires on the alternator. Im probaly going to have to take the whole s/c off.
 

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pinacup7 said:
I jumped it again then disconnected the negative terminal on the battery and the car died. Doesn't this confirm alternator?

Yikes- Not a good thing to do, and no- that test proves nothing. Dinner's ready, talk later. Proirities, you know...
 

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pinacup7 said:
I jumped it again then disconnected the negative terminal on the battery and the car died. Doesn't this confirm alternator?I also have a jrsc so its hard to get to the wires on the alternator. Im probaly going to have to take the whole s/c off. [/B]
I've done this with generators, if the engine was idling fast enough, but generators have permanent magnets and relays for voltage regulation. Alternators rely on battery voltage for field exitation and have solid state diodes to convert AC voltage to DC. I don't think alternators are as tolerant to "experimenting" as generators were.
 

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No, I it causes voltage spikes and so on that wouldn't phase a big old mechanical regulator, but could easily wreck anything solid state. Anyway, it's not necessary to do that. If your battery is at 12.6 and 13.7, that pretty much tells you the alternator is working.

Got the "only when in gear and under load" idea now. I don't know how that fits into all this.

All said and done, I'm going to stick by my original "major loose connection" theory because of the work/no work nature of this thing. Next time it happens try to get someone to hold the key in the "start" position and you go around and wiggle cables. Also, make sure that when you re-connected the negative terminal you pur everything back on. There's a little black/orange wire and maybe some other stuff.......
 

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Discussion Starter #8
UPDATE: My battery was bad and would not take a charge. Bad news - what I thought was my alternator making noise is my power steering pump.
 
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