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Discussion Starter · #1 ·
When jump starting a car that will not otherwise start, it turns over (didn't start yet). Windows, dash lights, radio all work... Jut not enough to start.

Friday, I had a trickle charger on it for 18 hours. Started like a champ, and died 18 miles from the house...

Car sat all summer... Had shop check it out, and change oil last week. They claim both are alt and batt are fine...

Planning to replace both anyway... Just wanted some expert opinions... :)
 

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Wire brush your connectors on the battery, and shoot some WD40 on them. If both the battery and alternator are good, you have a bad connection.
 

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If it dies while running and then doesn't have enough juice to restart, it's usually because the alt is bad and the car is running off of the battery until the battery runs out of juice. I would have the alt tested at AutoZone or Advance to double-check. I have run into no-start situations due to corrosion on the positive battery terminal also but it ran fine if you could get it to turn over.....
 

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Discussion Starter · #5 ·
If it dies while running and then doesn't have enough juice to restart, it's usually because the alt is bad and the car is running off of the battery until the battery runs out of juice. I would have the alt tested at AutoZone or Advance to double-check. I have run into no-start situations due to corrosion on the positive battery terminal also but it ran fine if you could get it to turn over.....
I follow thos thinking right up to the power windows and radio working... The battery hasn't enough juice to start the car, but the seat and windows work... I would expect it to be totally dead if you were driving on it... That is the confusion.

A car *should* be able to run on the alternator alone indefinitely... But the car died, and it only turns over with a jump, and the power accessories work...

I have no way of testing the battery for voltage, and don't know how old it is. Last shop to test both said they are both ok (I trust these people too)...

Bad connection is also a possibility...

Some sort of continuous draw could also be the problem...

I'll be running these down tomorrow...

It must be bad car month for me, because all 3 cars in my family are giving me grief!! Must be time to "test" me again... I'm trying to remember that "this too shall pass."
 

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Check your main engine ground. It could be corroded. That is also where your alternator runs its ground side.
 

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Follow the big black wire from your battery to the other end. There will be a bolt holding it to the engine block.
 

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Looks like at least one of your cars is a wagon. Check the auxiliary power post on the under-hood fuse box, under a black plastic cover. Battery positive goes here (follow the battery + lead if you don't know where it is) remove the black plastic cover just behind the under hood fuse box. If that threaded post is white metal you need to change it or get it changed. It will develop high resistance and ultimately melt and cause a fire. If the threaded post is yellow (brass) you are good to go.

Some 9C1s (I think 1995 & 1996, but I am not exactly sure) got the brass post but Civilian and 1994 did not.
 

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Discussion Starter · #11 ·
Looks like at least one of your cars is a wagon. Check the auxiliary power post on the under-hood fuse box, under a black plastic cover. Battery positive goes here (follow the battery + lead if you don't know where it is) remove the black plastic cover just behind the under hood fuse box. If that threaded post is white metal you need to change it or get it changed. It will develop high resistance and ultimately melt and cause a fire. If the threaded post is yellow (brass) you are good to go.

Some 9C1s (I think 1995 & 1996, but I am not exactly sure) got the brass post but Civilian and 1994 did not.

YIKES! Thanks GM!! Gives new meaning to "planned obsolescence!"
 

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To trouble shoot you need to take some voltage measurements, preferably when it's acting up. When it wont crank, measure battery post voltage while cranking if low, the battery is down and wiring is good, if post voltage is high then wiring is bad. With the motor running, measure battery posts voltage if greater than 14 volts, the alternator is good, replace battery. If running battery post voltage is below 13 volts alternator is bad, needs replaced.

____________________
source:
chilton auto repair manual
 

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do the big 3 and then see
 

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I would do voltage drop tests across ALT + to Battery +, ALT ground to engine, ALT ground to chassis, ALT ground to Battery -, Battery + to each cable off of Battery +, and Battery – to each cable off of Battery -. Here is a description of voltage drop testing http://www.engine-light-help.com/voltage-drop.html
 

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I guess I have the same problem I jump start my car and then it runs but the meter for the battery on the dash read negative!

Battery is still good less then 2 years optima yellow and the alternator is brand new just got it 2 weeks ago. Car runs but one head light goes out and and the battery reads negative right away if I stop the car the car runs slow, if I turn off the car it needs a jump start but then as soon as I turn it off it doesn't cut back on.

We checked everything it all looks good on connections.
 

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I guess I have the same problem I jump start my car and then it runs but the meter for the battery on the dash read negative!

Battery is still good less then 2 years optima yellow and the alternator is brand new just got it 2 weeks ago. Car runs but one head light goes out and and the battery reads negative right away if I stop the car the car runs slow, if I turn off the car it needs a jump start but then as soon as I turn it off it doesn't cut back on.

We checked everything it all looks good on connections.
Looking at it to check it is not good enough. Pull them off, and clean every connection. Very often the corrosion is not visible unless you pull the connection. Check both the positive and ground. Either one can be the culprit. You have a light that goes out, and your meter is not reading a charge. The light part can mean a ground or positive fault somewhere, especially when you are not getting a charge at the same time. It could be a loose wire, or even a malfunctioning voltage regulator in the alternator. Put a voltmeter on the circuit, and find out what is happening.

Try wiggling the wires while it is acting up. If it starts to act correctly, you have found the offending part, then all you have to do is check the connections and wire itself.
 

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Thanks for the input Fred If I don't find the problem today the car is going to my neighbor whose a 25 year mechanic lol But at least he charges half for neighborhood folks.


I'll check for corrosion for sure.
 
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