Car dies
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Staging Lane
Joined: Apr 2013
Posts: 53
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Car dies I have a 02 trans am, just replaced the alternator and battery is only about 4 months old and tested good. Well the car dies when the positive battery cable is disconnected. I changed the alternator 2 days ago because the car died and had to jump battery and such. What could the problem be? Or should the car die when it's disconnected from the positive side?
I've seen somebody twist the post on the back of the alternator while tightening the nut down and it ruins the alternator. Is it possible that you did that?
They should stay running when you remove the battery. I've actually undone a good battery while the cars running and swapped in a drained battery to charge it back up.
They should stay running when you remove the battery. I've actually undone a good battery while the cars running and swapped in a drained battery to charge it back up.
Teching In
Joined: May 2011
Posts: 20
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From: Northern Ohio
Unless you want to replace the PCM or other electronics, I don't recommend disconnecting the battery while running on a computer-controlled vehicle...the battery acts as an insulator. The PCM *may* be shutting the car down to protect itself from the voltage spike that you're creating by removing the insulator. On old cars, yes, if the car died when you disconnected the battery, the alt was bad...but that theory can't be used anymore with a PCM that has over-voltage protection, which most do.
Unless you want to replace the PCM or other electronics, I don't recommend disconnecting the battery while running on a computer-controlled vehicle...the battery acts as an insulator. The PCM *may* be shutting the car down to protect itself from the voltage spike that you're creating by removing the insulator. On old cars, yes, if the car died when you disconnected the battery, the alt was bad...but that theory can't be used anymore with a PCM that has over-voltage protection, which most do.
On another note I dropped a wrench and it got stuck between the posts, quite the spark show. Melted the wrench and the positive terminal on the battery and everything was fine. Everyone says I got lucky on that though.
To me 15 volts seems high, but it might be fine. Report back after you've checked the wires.
I have a 02 trans am, just replaced the alternator and battery is only about 4 months old and tested good. Well the car dies when the positive battery cable is disconnected. I changed the alternator 2 days ago because the car died and had to jump battery and such. What could the problem be? Or should the car die when it's disconnected from the positive side?
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Teching In
Joined: May 2011
Posts: 20
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From: Northern Ohio
Makes sense, but I've done it so many times I'm afraid I might have to learn that lesson the hard way. I tend to do that often.
On another note I dropped a wrench and it got stuck between the posts, quite the spark show. Melted the wrench and the positive terminal on the battery and everything was fine. Everyone says I got lucky on that though.
To me 15 volts seems high, but it might be fine. Report back after you've checked the wires.
On another note I dropped a wrench and it got stuck between the posts, quite the spark show. Melted the wrench and the positive terminal on the battery and everything was fine. Everyone says I got lucky on that though.
To me 15 volts seems high, but it might be fine. Report back after you've checked the wires.
I don't know what PCM's have over-voltage protection and which don't tho.15 volts is pretty high...esp. if the OP is using the dash gauge, as most of our volt gauges typically read low. A DVOM btwn ground and the pos. directly on the alternator would be the most accurate reading.
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I have a 02 trans am, just replaced the alternator and battery is only about 4 months old and tested good. Well the car dies when the positive battery cable is disconnected. I changed the alternator 2 days ago because the car died and had to jump battery and such. What could the problem be? Or should the car die when it's disconnected from the positive side?
I'm wondering if the exciter wire is broke or messed up.......
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Speak of the devil, on the rarity that this happens, had an 01/02 Caravan today that came in that cust. replaced the alt on himself...and had some issues afterwards. No locks, no radio, no heat, engine light random stuff...fixed the heat, locks, and radio with various blown fuses...engine light was a P0601 - internal PCM memory checksum error...fried the computer...and with this post still fresh in my mind, we got it out of him that he checked the alt the old fashioned way I don't know what PCM's have over-voltage protection and which don't tho.
I don't know what PCM's have over-voltage protection and which don't tho.I agree, my dash gauge typically reads 10 volts. But when you put when you put a DMM on like you said it reads around 13 - 14 volts.
Pop the two tops off, Look at the pin rows, look for any burnt pins. Tell tale sign its burning up on the inside.
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12 Second Club
Joined: Sep 2005
Posts: 4,273
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From: Bucks County, Pa.
I had the two connectors off, and ALL of the pins looked fine.
I even straightened out the red gaskets before putting everything back together with the correct torque setting.
Has ANYONE found those gaskets sold all by themselves, WITHOUT having to buy a whole new PCM????
I even straightened out the red gaskets before putting everything back together with the correct torque setting.
Has ANYONE found those gaskets sold all by themselves, WITHOUT having to buy a whole new PCM????
Teching In
Joined: May 2011
Posts: 20
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From: Northern Ohio