blown alternator while trying to jump start?

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Pyromidion

Senior member
Aug 22, 2001
236
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Hello there,

Yesterday at work, I had a woman request a jump start for her car. (the lights were left on, but isn't it true that newer cars automatically shut the lights off if the car is off??) I called on the maintenance / security pickup to come around with the jumper cables, and we hooked it up and got nothing.

A 2nd try (with the +/- cables switched!) made the wipers and horn go off, but still no start. (I saw the guy put the + cable on the - battery terminal and asked "are you sure thats right?", he said "yea, yea")

a 3rd try resulted in the car starting, and she pumped the revvs between 3-5k for a minute or so, but the moment we took the cables off the battery, it sputtered and stalled out.

a 4th try (started up) I noticed that the battery icon on her dash was lit, and mentioned that it may be the alternator not charging the battery, but she said that the car was too new, and that couldn't be the problem. AAA was called, and indeed it was the alternator (returning 0v) at fault.

so the question is, was there something in the jump-start (perhaps switching the cables!?) that could blow the alternator, or was the poor thing on its way out to begin with?

-John
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,576
126
Cars don't necessarily shut the headlights off automatically. Many cars don't have the auto headlights at all, and if they do, you usually have to turn it to auto.

They all beep and chime like crazy if you leave them on, though. :D

Yes, hooking the cables up backwards probably did all sorts of damage to all sorts of things.
 

Baked

Lifer
Dec 28, 2004
36,052
17
81
There are somethings better off left to the professionals. I've jumped started many coed's dead cars back in college and have never ran into a blown alternator. OP = man fail.
 

StageLeft

No Lifer
Sep 29, 2000
70,150
5
0
Originally posted by: Baked
There are somethings better off left to the professionals. I've jumped started many coed's dead cars back in college and have never ran into a blown alternator. OP = man fail.
I don't think cars are jumpable as easily as they used to be. After my experience with my MPV and a guy at work's M3, there is just something off about the whole thing.

 

EightySix Four

Diamond Member
Jul 17, 2004
5,122
52
91
Originally posted by: Skoorb
Originally posted by: Baked
There are somethings better off left to the professionals. I've jumped started many coed's dead cars back in college and have never ran into a blown alternator. OP = man fail.
I don't think cars are jumpable as easily as they used to be. After my experience with my MPV and a guy at work's M3, there is just something off about the whole thing.

This.

Some cars do not like to be jump started at all, especially some with the newer PCM's, if it doesn't get quite enough voltage at start, it isn't going to happen.
 

lsd

Golden Member
Sep 26, 2000
1,184
70
91
Yes its possible the alternator diode pack was burnt if indeed the polarity was switched. But I would imagine a whole slew of other fuses/ fusible links would be burnt.
 

Savij

Diamond Member
Nov 12, 2001
4,233
0
71
Originally posted by: Pyromidion
Hello there,

Yesterday at work, I had a woman request a jump start for her car. (the lights were left on, but isn't it true that newer cars automatically shut the lights off if the car is off??) I called on the maintenance / security pickup to come around with the jumper cables, and we hooked it up and got nothing.

A 2nd try (with the +/- cables switched!) made the wipers and horn go off, but still no start. (I saw the guy put the + cable on the - battery terminal and asked "are you sure thats right?", he said "yea, yea")

a 3rd try resulted in the car starting, and she pumped the revvs between 3-5k for a minute or so, but the moment we took the cables off the battery, it sputtered and stalled out.

a 4th try (started up) I noticed that the battery icon on her dash was lit, and mentioned that it may be the alternator not charging the battery, but she said that the car was too new, and that couldn't be the problem. AAA was called, and indeed it was the alternator (returning 0v) at fault.

so the question is, was there something in the jump-start (perhaps switching the cables!?) that could blow the alternator, or was the poor thing on its way out to begin with?

-John

Everyone involved should turn in their man cards! I know jack shit about cars and I know better than that.
 

nakedfrog

No Lifer
Apr 3, 2001
62,822
19,026
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The negative cable isn't even supposed to be hooked to the battery at all. It's supposed to be attached to an unpainted piece of metal somewhere in the engine bay. Yes, switching them is not good.
 
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