w202 jumpstart gone wrong - have i killed the altenator ?

anyweb

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wife needed my car again today (w202-1995) but complained that the door wouldn't open, indeed it wouldnt as the battery was flat, she left the lights on when she locked it the day before...

so i attempted to jump start it for the first time in a few years and made the mistake of connecting the two cables which connect directly to the altenator to the plus/minus on the jumpstart cables to my other car,

there was some electrical smoke and i adjusted the cables slightly before trying again, same thing *but car lights did come on during this)

so, i disconnected the cables quickly and felt stupid... now perhaps my altenator is fried ??? who knows

next i read this post which correctly showed where the PLUS was on my car, (see the yellow arrow in the attached pic below)

i conencted up plus to that and connected minus to an earth point on the car (a bare screw..) this time when i started the car it fired up immediately no problem at all, BUT when i diconnected either plus or minus the car died immediately. I attempted this again with the same result, the car starts just fine when i have the jump start cables attached but as soon as i remove one, the car dies.

so have i killed the altenator or do I just need to charge the battery ???? is there something in the altenator that can be quickly and cheaply replaced as it was perfect before i messed things up :(

so frustrating arghhhhhhhhhhhhhhhhhh
 

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television

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No this should not be the alternator, this could be a totally flat battery or you have blown one of the earth wires, or maybe the connection in the box where you joined up incorrectly
 

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What you need to do Niall is to put a voltmeter on the terminal block where you jumped from, there should be 12 volt on it, no 12 volt if the battery has 12volt in it, then a connection blown or ground wire
 
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well i've removed the battery and it's on a charger now, i'll leave it there for as many hours as i can before reattaching and attempting to start the car again, wish me luck

just to re-iterate what i did inittially

i connected jump start wires (plus and minus) directly to the TWO ouput wires on my alternator (dumb i guess) and it was at that moment that smoke started, hence me worrying that i've fried the alternator

only later when i tried to connect the wires PROPERLY to te plus *as marked in the photo) and ground (ground on the car) did the car start correctly, but then abrubtly died when i removed either of the jump start cables

so is my only problem that the battery is DEAD flat ?
 

whitenemesis

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It is my understanding the car does not use the battery once running, all power comes from the alternator, any surplus goes to charge the battery.

It sounds like you have blown the regulator pack on the alternator.
 
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and that is my worst fear, is that easy to replace ? does this explain why the car DIES once i remove the jump cables ?
 

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and that is my worst fear, is that easy to replace ? does this explain why the car DIES once i remove the jump cables ?

How much you will need to replace depends on how much damage you have done. and yes,if it was charging,the car should continue to run even if the battery was totally flat.
However,there is the outside chance that there wasn't enough in the battery to activate the alternator,so don't give up hope just yet.

I would expect that when you refit your charged battery,the car will start and run.If there is no warning light on the dashboard,switch on the interior light and keep an eye on it while you start the engine.
If it is charging,it should become noticeably brighter when the engine starts,or similarly,noticeably dimmer after you have stopped it.

Regards,
Nick.
 

whitenemesis

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I think Malcolm posted something about replacing reg packs. I'm not sure how simple it is. Generally one replaces the alternator complete, swapping with a recon unit.
 
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ok update, i reattached the battery aafter charging it externally for a bit (2 hours) and now the car is starting fine and staying on, so, i don't know if this means that all is ok (will know soon enough i guess) of if the alternator is still not ok,

i'll pray and hope for the best, but for now, i'm very happy that the car is starting and staying on
 

whitenemesis

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ok update, i reattached the battery aafter charging it externally for a bit (2 hours) and now the car is starting fine and staying on, so, i don't know if this means that all is ok (will know soon enough i guess) of if the alternator is still not ok,

i'll pray and hope for the best, but for now, i'm very happy that the car is starting and staying on

Fingers crossed ;)
 

Alex Crow

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does the battery light come on before starting, and go out when started? or does it not come on at all? what voltage do you see when running?
 

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Cars runs on the battery or alternator as they are both connected in parallel, if the alternator is not working, then the warning lamp should be on, if they warning lamp is on when you turn the key to ignition, then the bulb is ok.

The difference between the battery (12.5v) and the alternator (13.8 V) is that if the alternator is working, the car runs on the alternator as that has the highest voltage.

You may have blown the warning bulb that is in the exciter lead from the alternator or the reg pack, these only cost £12 and are held on with 2 screws, dead easy to change and this will not have blown the whole alternator
 
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ok took it for a drive, no charge, the alternator is dead, my local indie found a replacement 2nd hand one for 100 quid, so i'll let him replace it

it sux, but i've learnt a valuable lesson...

cheers
niall
 

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ok took it for a drive, no charge, the alternator is dead, my local indie found a replacement 2nd hand one for 100 quid, so i'll let him replace it

it sux, but i've learnt a valuable lesson...

cheers
niall

It will still only be the reg pack that has blown
 

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Hope you kept the old one as a spare. Easy to rebuild with a new rectifier pack off the car.
 

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just to re-iterate what i did inittially

i connected jump start wires (plus and minus) directly to the TWO ouput wires on my alternator (dumb i guess) and it was at that moment that smoke started, hence me worrying that i've fried the alternator
It would as the thinner wire is Gnd to trigger the warning lamp.

Alternators use the alternator body and engine block as the Gnd connection and the thicker wire to the battery +ve, though that wouldn't be beefy enough to start the engine by.

Fried regulator pack....easy to change.
 

dbanbery

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i agree with the other the regulator pack sits on the back of the alternator and is an easy replacement [IIRC]

i've always jump started cars off the battery in the boot??? didnt know there were contacts under the bonnet!!?
 
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ok anyone know where the reg pack replacement guide is here ? i'm back from vacation so that's my excuse and my car is still dead, seems the altenator the indie sourced was crap so he didnt get it, so i need to fix mine asap
 

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Just go to any Bosch agent,,only 2 screws holding it in and dead cheap, even in Sweden,,I changed loads when I lived there owing to the amount of electronic gear installed in the Swedish radio cars
 

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Lots of videos on Utube about this. http://www.youtube.com/watch?v=vTmDBCAZyCQ&feature=channel Slight variations from vehicle to vehicle but principles the same. Make sure you disconnect the battery first. Be methodical taking it apart- take some pics with a digital camera then just replace the faulty components in reverse of dismantling. If unsure just dismount from the car and take to your local Vehicle electrician /agent who will rebuild it for you.
 
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