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  #1  
Old 28th May 2007
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Unhappy A serious electrical problem?…wrong battery polarity

Hi,
Well I do feel sick about this self inflicted issue which I can only hope has caused no damage afterall. Your opinions greatly appreciated.
The issue being that I incorrectly connected the battery, ie negative ground to positive.
Sequence as follows,
1. Connected positive harness to negative terminal.
2. Placed negative ground to positive terminal. Sparks followed, did not force a connection. Placed a second time [thinking it was an open circuit issue] but surprised by the degree of reaction and withdrew the lead then spotted the cause. All this was momentary~say a second in duration.
3. Then switched battery around and connected the positive followed by negative. Sparks again. These were momentary, I did not force the matter.
4. Put battery on charge, seemingly now low. Since fully charged, according to battery charger.
5.Panicked…felt numb…made straight to post this SOS

Should say ignition was OFF, only circuit open as far as I can reakon is the Clock and Alarm.

So, what sort of damage may have been caused, is there anything thing I should do~check before installing the battery again?
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  #2  
Old 28th May 2007
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Quote:
Originally Posted by finbarr
Hi,
Well I do feel sick about this self inflicted issue which I can only hope has caused no damage afterall. Your opinions greatly appreciated.
The issue being that I incorrectly connected the battery, ie negative ground to positive.
Sequence as follows,
1. Connected positive harness to negative terminal.
2. Placed negative ground to positive terminal. Sparks followed, did not force a connection. Placed a second time [thinking it was an open circuit issue] but surprised by the degree of reaction and withdrew the lead then spotted the cause. All this was momentary~say a second in duration.
3. Then switched battery around and connected the positive followed by negative. Sparks again. These were momentary, I did not force the matter.
4. Put battery on charge, seemingly now low. Since fully charged, according to battery charger.
5.Panicked…felt numb…made straight to post this SOS

Should say ignition was OFF, only circuit open as far as I can reakon is the Clock and Alarm.

So, what sort of damage may have been caused, is there anything thing I should do~check before installing the battery again?
It's something anyone could do - simple things always cause the most grief!

That aside, what could be damaged depends on the amount of electronics in the car mostly, and secondly if the earth points are all good, since limitations on short circuits come from the amount of resistance present.

I doubt that a momentary reverse-polarity connection will kill the battery itself - you can always check it's terminal voltage after letting it sit overnight after a charging cycle and see if it's still 12.5 volts or above.

Stuff like the stereo, etc. may be fried though again it all depends. Some devices might be able to handle reverse-polarity power connections if they were connected to power and earth at the time (the other way around!).

The best way to be safe is get an auto-electrician who knows about Saab's to check the car thoroughly. Even if you re-connect the battery the right way around, you could have created shorts inside electronic devices which will cause more damage when the correct polarity power connection is made to the car's electrics.

I hope your car is ok. Treat it as a learning experience since you'll remember it for a very long time, and you can teach other people the importance of installing batteries the right way around.

Craig.
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  #3  
Old 28th May 2007
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You can blow a few fuses but it sounds like you didn't force the connection for any length of time, you should be ok according to me

You Panic easy or what

I once had a jammed starter motor on a tracktor, it caught fire and was smoking like crazy, I pulled the lead wire to the soleniod and it was still blazing, I then yanked the whole battery cable off pulling the positive terminal with it fun and games man, fun and games
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  #4  
Old 28th May 2007
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IIRC, all electronic units, except central locking (and radio) are on switched wire, so they should stay intact from reverse polarity.
Put a battery in car (correctly, please ) and try lock and unlock, if it will work, then go further - switch key into ACC and try radio, if OK switch to ON and look for control lights, try headlights, brakes (if You have ABS), all systems of car and if everything is OK, then start it.
Clasic 900 has not so much special electronic like a new 9-5 or 9-3, so risk of completely damaged electrical system is much less than at those ones.
One good thing is, that most of electronic devices have a diode, what should protect them from reverse polarity.
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  #5  
Old 28th May 2007
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Quote:
Originally Posted by misu
IIRC, all electronic units, except central locking (and radio) are on switched wire, so they should stay intact from reverse polarity.
Put a battery in car (correctly, please ) and try lock and unlock, if it will work, then go further - switch key into ACC and try radio, if OK switch to ON and look for control lights, try headlights, brakes (if You have ABS), all systems of car and if everything is OK, then start it.
Clasic 900 has not so much special electronic like a new 9-5 or 9-3, so risk of completely damaged electrical system is much less than at those ones.
One good thing is, that most of electronic devices have a diode, what should protect them from reverse polarity.
Yes that's generally true and you're probably right that the lack of electronics in the older 900's means reverse-polarity battery connection is less likely to cause problems.

Still the cautious approach is best, and if anything at all doesn't go right when the battery is re-connected and the various car systems are tested, consult with an auto-electrician. If the engine will crank and run, I guess the car is mostly ok. Checking that relays (some of which do contain electronics inside the casing) and fuses are not damaged will probably be the main area that's good for tell-tales about what might have been affected.

Craig.
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  #6  
Old 28th May 2007
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Yes, relays with electronic! Like time delayed interior light! This relay is also "live" all the time, so it should be first check.
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  #7  
Old 28th May 2007
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The first thing I would check once you have started the car is the alternator.


Rectifiers (diode bridge) don't take kindly to reverse polarity. and can go open if the terminals were hooked up long enough. sounds like you may have escaped unscathed with two momentary contacts though.

connect the battery properly, start the car, and see if the alternator is charging. should be around 12.5 volts off, and 13-14 volts running.

two momentary contacts will not kill a battery...
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  #8  
Old 28th May 2007
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Yeah the worst likely damage is a fried alternator diode pack. They don't really wear so if you have a dead alternator somewhere you can swap it.
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  #9  
Old 29th May 2007
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Well, I hate to admit I did this exact same thing with my Porsche 914 not too long ago. I fried the diodes in the alternator, as has been stated as a possibility in earlier posts. My alternator light would stay on even if the key was not in the car.

Thankfully, if this did happen to you, you are alot better off as an alternator, painful as it may be in a 900 to replace, is a heck of alot easier than changing a 914's alternator! Ugh. I just got it back on the road yesterday.

Good luck, maybe you're OK. But if your alt light stays on, maybe the diodes are gone. (I replaced the voltage regulator also, just to be safe.)

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  #10  
Old 29th May 2007
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Easily done,

(Must be cos I did it too! ).

Only issue for me was the alternator got fried, and had to be replaced, so get that checked out ASAP.
Cost me £250 to get a new one fitted, I don't know if that means I was done over or not??
Interestingly though, until I had the new one fitted, I never saw the "battery" light on the dashboard when the key is put in.

Mark
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  #11  
Old 29th May 2007
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i did it a while ago to a mazda 121. Ijust blew the main fuse of which there were two. It looked like a light weight cable and about 2 centimetres long. I wound it back together and drove down and got another one.Doesn't the 900 have a main fuse?


You will nedd tolook at a circuit diagram.

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  #12  
Old 29th May 2007
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heh ... he just thought he was putting the battery into a mid 60's Triumph ... I have many "fond" memories of my Herald ...
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  #13  
Old 29th May 2007
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On my car there is a WARNING label on the FR wheel arch just above the battery. It says that the alternator will be destroyed if you incorrectly connect the battery.

It's a bit late now, but have a look at the WARNING label on your car if it has not been removed.
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  #14  
Old 29th May 2007
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Quote:
Originally Posted by ShadowWorks
You Panic easy or what
doesn't feel like that…but probably because it may be my norm …frazzled raw nerves…off to replenish my supply of brandy and honey as a have a bug for company at the moment.
Many thanks for your take on this and kind reassurances that "its just not me". Seems I might well expect something…alternator seemingly {RedRag…I suspect the volt regulator/brushes (is the diode in that?) are available as a seperate part but not necessarily from SAAB, depends on which AMP altternator}…this electronics thing in newer cars is a ransom.

Steve…Triumph Herald!…scarsely see those around, have a certain fondness for them too…can still see the occassional trooper on the road.

Will sort the car out in a few hours time.
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  #15  
Old 29th May 2007
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Quote:
Originally Posted by finbarr
Steve…Triumph Herald!…scarsely see those around, have a certain fondness for them too….
it was a cool little car - right hand drive over here in the states tends to attract attention (mine was RHD) - I haven't seen one on the road in years (although I know where a LHD "project" currently resides) - every once in a while you'll get to see one on shows like "last of the summer wine" - and in one old James Bond film as well (Dr. No, I believe).

Best of luck with your problem - chances are if it took out anything it was the diode pack in the alternator - standard Bosch item I believe. The sparks are exciting, no?
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  #16  
Old 31st May 2007
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Default alternator got fried, maybe battery but how to remove alternator?

rather like a caricature of a comedy sketch in a Michael Bentine –ish way there was……quite a big spark……a deep pop (as in bottle cork)……a small beep blue & well formed puff~cloud of smoke……and finished off with a passing wiff of something very much over fried……all in that order.
And that was it. No more sparks. Connected up, battery read 12.5V, instrument lights except Battery illuminated, engine Started first go in usual manner, at idle ~12.25V, at 2500rpm ~12.75V (on another try ~13.25V / ~13.75V) so ~0.5V gain on charging. Down on 14.0V but it would be down since Battery instru. bulb is apparently blown (to be checked yet)…ref. Bentley's.
I will be taking more readings as per Bentleys soon. Yet to be resolved.
So still working after a fashion with no failures elsewhere.

Battery now drained overnight so perhaps damaged alternator created a closed circuit and drained the battery overnight (I hope otherwise I have a fried battery as well )
so now to reomve alternator……
but how best?
if removing as Bentleys that means the Hex bolts holding the bracket to the engine block. The one they photo'd looks do-able but the other one the has very much more restricted access do to closeness to alternator and is a real problem…which sort of tool is required for that?……or would the alternator be easier removed by taking out the 'hinge' bolt but then there are the bushing to mess with…oh, I dont know, brain now ceased up.




footnote…spotted the alternator removal note in forum faq…but those Allen hex bolts are quite small and I suspect that they may well be on very hard plus access not too good……is there any technique to deal with this apart from liberal use of WD40 to ease them before I round off the internal hex ?

Last edited by finbarr; 31st May 2007 at 07:39 PM. Reason: add footnote
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  #17  
Old 1st June 2007
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IIRC, when i swapped out my alt. I had a heck of a time getting the bolt that holds the thing out all the way. I had to bang a dent into the firewall to get the danged all the way out. I thought I was doing it the wrong way, but there was already a big dent there; someone must have had the same issue.

It really wasnt that hard, check the alt. bushings while you're at it.
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Old 1st June 2007
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Quote:
Originally Posted by finbarr

footnote…spotted the alternator removal note in forum faq…but those Allen hex bolts are quite small and I suspect that they may well be on very hard plus access not too good……is there any technique to deal with this apart from liberal use of WD40 to ease them before I round off the internal hex ?
I used Allen hex head socket on wobble extension bars.

Last edited by RickyS; 2nd June 2007 at 05:20 AM.
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  #19  
Old 1st June 2007
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Quote:
Originally Posted by DanF.
I had a heck of a time getting the bolt that holds the thing out all the way. I had to bang a dent into the firewall to get the danged all the way out. I thought I was doing it the wrong way, but there was already a big dent there; someone must have had the same issue.
Do NOT try to remove the long mounting bolt in the car. Remove the bracket with the alternator, install new bushings on the bench before refitting the assembly. There is nothing to be gained by leaving the bracket on the car, and a dented firewall just gives long-lasting evidence of shoddy work.
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  #20  
Old 1st June 2007
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Experience comes from bad judgment.



Where were you when I needed you most Jim? jk
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