Wired battery in reverse, lots of smoke, what is the best case scenario

[repenttokyo]

So in the dark snowstorm tonight I connected a new optima redtop battery in reverse. It was sparking a bit as I tightened it, but I thought it was due to the water from all the melting snow. Then the negative cable (connected to the pos) started to smoke, and then I started to get smokw from under the firewall and from under the intake cover, i took loosened like a madman and pulled it off and doused it with an extinguisher for 2 secs just in case, but now the **** has hit the fan.

I of course put the battery back in the right way, tried to start, nothing. I also tried to jump the car, no power to the starter whatsoever.

No dome light, the sunroof opened itself (lifted up), I have power to the headlights and stuff, radio, dash all works, but no starter turning.

So how screwed am I? What are the chances that I burned out a significant chunk of wiring / ECU? Or have fuses saved my ass? Under the hood, the small fuses all looked ok. Haven't been able to check the big fuses - had to shovel and then push the car into the garage since the sunroof is now open.

Ideas?

[whiskychaser]

So in the dark snowstorm tonight I connected a new optima redtop battery in reverse. It was sparking a bit as I tightened it, but I thought it was due to the water from all the melting snow. Then the negative cable (connected to the pos) started to smoke, and then I started to get smokw from under the firewall and from under the intake cover, i took loosened like a madman and pulled it off and doused it with an extinguisher for 2 secs just in case, but now the **** has hit the fan.

I of course put the battery back in the right way, tried to start, nothing. I also tried to jump the car, no power to the starter whatsoever.

No dome light, the sunroof opened itself (lifted up), I have power to the headlights and stuff, radio, dash all works, but no starter turning.

So how screwed am I? What are the chances that I burned out a significant chunk of wiring / ECU? Or have fuses saved my ass? Under the hood, the small fuses all looked ok. Haven't been able to check the big fuses - had to shovel and then push the car into the garage since the sunroof is now open.

Ideas?

My guess is your alternator is toast for a start. Radio too unless its got an 'idiot diode' in it. If the 'new' battery is still functioning, I'd connect up and see what still works when you get the chance. Unlucky :(

[Paul in NZ]

would the fusible link have sacrificed itself?

[ryan roopnarine]

not to threadjack, but how did you get the connectors to reach the opposite pole? did you put the battery in the hole backwards? i know that the wires in my underseat mounted 1992 525i won't reach all the way over.

[tim eh?]

damn - sympathies man that's unlucky.

i was present at a boost gone bad once, the cables were crossed (wasn't me or my car). lots of smoke - kinda scary pulling the cables off. (think fast - which cable do you take off first?) no damage to either car, hopefully that bodes well for you.

the fusible links aren't inline with the starter, they only protect the vehicle electrical system. so the sunroof doesn't close now?

so you boosted from another source? maybe your "new" battery is cooked and won't pass enough charge anymore? have you tried another battery?
i would also check the thick battery cable for signs of being cooked.


good luck ben, that is a bummer.

[repenttokyo]

My guess is your alternator is toast for a start. Radio too unless its got an 'idiot diode' in it. If the 'new' battery is still functioning, I'd connect up and see what still works when you get the chance. Unlucky :(

radio works, headlights work, interior dash lights work but dome light does not.

sunroof will not tilt back down - is there an emergency procedure to close the sunroof?

I'm going to be out of town for a week, so the car is just sitting in my garage at this point. I am worried that things are really toast in the wiring harness, and possibly the ECU.

It's less unlucky than REALLY STUPID on my part. I am so upset at myself, it's unbelievable. I am heading back to Canada tomorrow, and instead of driving my own car I will now be hitching a ride with my parents, who had come down to visit for the weekend. I feel ashamed.

[repenttokyo]

not to threadjack, but how did you get the connectors to reach the opposite pole? did you put the battery in the hole backwards? i know that the wires in my underseat mounted 1992 525i won't reach all the way over.

my battery is not under the seat.

[repenttokyo]

damn - sympathies man that's unlucky.

i was present at a boost gone bad once, the cables were crossed (wasn't me or my car). lots of smoke - kinda scary pulling the cables off. (think fast - which cable do you take off first?) no damage to either car, hopefully that bodes well for you.

the fusible links aren't inline with the starter, they only protect the vehicle electrical system. so the sunroof doesn't close now?

so you boosted from another source? maybe your "new" battery is cooked and won't pass enough charge anymore? have you tried another battery?
i would also check the thick battery cable for signs of being cooked.


good luck ben, that is a bummer.


I am a total retard. no offense to any retards who might reading this.

[BMWDriver]

Gosh, too bad. At least the whole electrical system is not all toast.

Yes, you can close the roof. There is a small panel that you remove right by the cabin lights (dome lights), and it requires a hex key shaped as a "Z" more or less. That should be in your toolkit in the back, provided it's still there. Otherwise it's just a matter of having the right size.

Good luck !

[632 Regal]

Dude stuff still works! that is a great thing for sure!! eliminate the nasties from the realies and then repost, I dont thing you did too bad yet.


radio works, headlights work, interior dash lights work but dome light does not.

sunroof will not tilt back down - is there an emergency procedure to close the sunroof?

I'm going to be out of town for a week, so the car is just sitting in my garage at this point. I am worried that things are really toast in the wiring harness, and possibly the ECU.

It's less unlucky than REALLY STUPID on my part. I am so upset at myself, it's unbelievable. I am heading back to Canada tomorrow, and instead of driving my own car I will now be hitching a ride with my parents, who had come down to visit for the weekend. I feel ashamed.

[attack eagle]

sounds like the gm is toast... and more of course.

[repenttokyo]

Leaving for a week, so I won't be able to look at the car again until next monday at the earliest. I will post back when I have a more thorough diagnosis of what works / what doesn't.

[whiskychaser]

Leaving for a week, so I won't be able to look at the car again until next monday at the earliest. I will post back when I have a more thorough diagnosis of what works / what doesn't.
Not much consolation, but I reckon we are all guility of making a mistake we could kick ourselves for at some time or other. Hope you have a good holiday and come back refreshed and ready for the challenge

[Ross]

Don't beat yourself up.
Alternator or at least the regulator are prob junk as is the smoking cables. Maybe the LKM and GM too. Little else would have seen power unless you turned the car on.
All that stuff is plentiful and hope fully no wires in inaccessible places were burned. I've lots of stuff from my '94 parts car left, let me know if you need anything that might interchange.
I understand that feeling when the smoke starts. Once I used a too tall battery in a 750, when someone sat on the rear seat it shorted causing smoke to start billowing from beneath the seat. Shogun would have been very impressed with how quickly I managed to remove that rear power seat.

[Jehu]

Don't beat yourself up.
Alternator or at least the regulator are prob junk as is the smoking cables. Maybe the LKM and GM too. Little else would have seen power unless you turned the car on.
All that stuff is plentiful and hope fully no wires in inaccessible places were burned. I've lots of stuff from my '94 parts car left, let me know if you need anything that might interchange.
I understand that feeling when the smoke starts. Once I used a too tall battery in a 750, when someone sat on the rear seat it shorted causing smoke to start billowing from beneath the seat. Shogun would have been very impressed with how quickly I managed to remove that rear power seat.


How much taller than the original was this battery? I just last week bought one that was taller than what was in there and I had to re-bend the brass strap to have it fasten to the body ... I rarely have passengers in the back but ... I went to an Interstate Store to buy an Interstate Megatron. I was not concerned about price but the sales guy showed me a battery with the same power rating as the Megatron that he said was from the stock of an auto parts store which liquidated and I could buy it with a 12 month replacement warranty and could within that time trade up to the Megatron if i want.. cost? $45.00.. his argument was even if it only lasted a year you could buy one a year for the next three years still for less than the Megatron.. the seat snapped down fine but I'd say the battery was at least an inch taller..

[Ferret]

Not much consolation, but I reckon we are all guility of making a mistake we could kick ourselves for at some time or other. Hope you have a good holiday and come back refreshed and ready for the challenge

I've seen this happen before, on a much less technologically advanced car.

The rectifiers in your alternator are burned to a crisp by now, as well as the regulator. Bin the whole alternator and dont attempt to save it - even if you can get the solid state bits back into good shape there's a good chance some of the windings are toast. Disconnect it totally from the loom while you're problem solving - there's a good chance it'll have its rectifiers conducting bi-directionally, meaning it's sinking current the whole time the battery is connected the right way around.

Your alternator and starter use the same rough loom - which is probably going to need to be replaced - scrapheap challenge time there. This means your starter motor is probably currently disabled with a burned loom.

You'll need to check every system that runs without the key in the ignition - your dome lamp not functioning is a good indication that the body electronics have been disabled... I cant remember reading it, but did you check the fuses under the rear seat? Do your windscreen wipers work? I seem to remember them being electrically similar for their feeds, meaning if the GM/body electrics have been taken out they'll stop working. It'll also disable your door locks and electric windows.

Grab a replacement body computer out of a scrapper, and drop it straight in.

Your engine ECUs etc /should/ be okay as they should be electrically isolated from the battery feed on at least one side, so shouldnt have had reverse current through them.

Check your fusible link *very* carefully, and electrically check every other fuse on the vehicle - if something was really going for a burn out, a fuse should have saved it...

[Claude]

So in the dark snowstorm tonight I connected a new optima redtop battery in reverse. It was sparking a bit as I tightened it, but I thought it was due to the water from all the melting snow. Then the negative cable (connected to the pos) started to smoke, and then I started to get smokw from under the firewall and from under the intake cover, i took loosened like a madman and pulled it off and doused it with an extinguisher for 2 secs just in case, but now the **** has hit the fan.

I of course put the battery back in the right way, tried to start, nothing. I also tried to jump the car, no power to the starter whatsoever.

No dome light, the sunroof opened itself (lifted up), I have power to the headlights and stuff, radio, dash all works, but no starter turning.

So how screwed am I? What are the chances that I burned out a significant chunk of wiring / ECU? Or have fuses saved my ass? Under the hood, the small fuses all looked ok. Haven't been able to check the big fuses - had to shovel and then push the car into the garage since the sunroof is now open.

Ideas?

I tried to figure out how the battery cable could "smoke" or burn and some others under the intake manifold as you write.
QUESTION: did you in fact, first place, connect your new battery in parallel with the old one but with wrong polarity (sort of jumpstart from your new battery) and fixing the ground lead from the new battery (the one you thought was the negative) to the engine bloc instead of directly to the negative pole of the old battery ? Doing so would for sure have produce large amount of current in between the two batteries (kind of shortcircuiting the batteries from one to the other THROUGH the grounding circuit... grd cabling of the car). If you just replaced the old battery with the new one connecting the car battery cables to the wrong pole, i can't explain the amount of dissipated energy you described.

[repenttokyo]

I tried to figure out how the battery cable could "smoke" or burn and some others under the intake manifold as you write.
QUESTION: did you in fact, first place, connect your new battery in parallel with the old one but with wrong polarity (sort of jumpstart from your new battery) and fixing the ground lead from the new battery (the one you thought was the negative) to the engine bloc instead of directly to the negative pole of the old battery ? Doing so would for sure have produce large amount of current in between the two batteries (kind of shortcircuiting the batteries from one to the other THROUGH the grounding circuit... grd cabling of the car). If you just replaced the old battery with the new one connecting the car battery cables to the wrong pole, i can't explain the amount of dissipated energy you described.

hmmm, not sure if i understand the scenario you are describing but no, only one battery at a a time.

[Ferret]

I tried to figure out how the battery cable could "smoke" or burn and some others under the intake manifold as you write.
QUESTION: did you in fact, first place, connect your new battery in parallel with the old one but with wrong polarity (sort of jumpstart from your new battery) and fixing the ground lead from the new battery (the one you thought was the negative) to the engine bloc instead of directly to the negative pole of the old battery ? Doing so would for sure have produce large amount of current in between the two batteries (kind of shortcircuiting the batteries from one to the other THROUGH the grounding circuit... grd cabling of the car). If you just replaced the old battery with the new one connecting the car battery cables to the wrong pole, i can't explain the amount of dissipated energy you described.

It's the alternator...

When you connect the battery the right way around, it's internal rectifier is aligned such that it's blocking current from flowing backwards through the alternators windings.

When you connect the battery the wrong way around, the rectifier is aligned such that it's encouraging current to flow the right way around the alternator, but seeing as the battery is plugged in the wrong way, it can now /drive/ current around the alternators wiring.

The problem comes from the fact that an alternator is designed to cope with upto 115/150Amps AC being internally driven, which means its internal resistance has to be very low... if you hook up the battery the wrong way around, the alternator is going to consume a hell of a lot of power in direct current, probably more power than the starter motor could. Of course, the loom isn't designed to cope with this scenario - and the smoke is the wiring overheating and burning out.

Other electrical devices such as the body computer, while they /should/ have reverse polarity blocking diodes in them, quite often don't as a cost saving measure... after all it's more profitable to the car manufacturer if a customer accidentally wires the battery backwards.

[Ross]

Not to worry in your 5'er. If the seat clears you are okay.
In the 750s the rear seats are power and have a metal bottom. the battery I used was a temporary fix that was WAY off.
Be sure the battery you bought has the proper vent with the tube connected.

[repenttokyo]

Ok got some good news. Apparently the only thing that needs to be replaced is the starter and the negative battery cable. That, in addition to a few fuses. How lucky am I? I should get the car back tomorrow.

[632 Regal]

That would be VERY lucky in my book!!!


Ok got some good news. Apparently the only thing that needs to be replaced is the starter and the negative battery cable. That, in addition to a few fuses. How lucky am I? I should get the car back tomorrow.

[Ross]

From the scenario you described I cannot fathom how the starter was damaged.
Someone tell me what I'm missing.

[repenttokyo]

That would be VERY lucky in my book!!!

I am hoping that there are no hidden issues, like a weakened alternator that will leave me stranded at some point - I guess only time will tell. Although, if the garage suspected the alt was bad, then they would certainly charge me to replace it - I mean, cash in their pocket, right?

They also told me my guibo was cracked, but hey, pretty sure it's been like that since I bought the car.

[pingu]

Ross, I agree - while I could understand Ferret's explanation of why the alternator could well be toast (due to the diodes conducting), the starter is just a bloody great motor with a bloody great solenoid.

I can see how the battery negative cable could have become fried but not how the starter would too...

[repenttokyo]

From the scenario you described I cannot fathom how the starter was damaged.
Someone tell me what I'm missing.


he tried powering the starter directly and no dice - it didn't crank.

could the heat have caused the starter to fuse internally?

[Ross]

he tried powering the starter directly and no dice - it didn't crank.

could the heat have caused the starter to fuse internally?

like I said it's inconcievable to me how this would be a direct result of reversed polarity, even if the starter had been engaged I think it would just merrily spin backwards.

[repenttokyo]

More bad news:

Starter was replaced, but alternator is failing a charge test and shows a bad diode. Garage wants way too much for an alternator ($671 installed) compared to what I could one for at BMA, so I am considering taking the car back and doing it myself - especially since the car currently runs and drives.

But that's not the bad part - the car is also running on 5-cylinder. He says that there is an output stage error and an injector error. He wants to do an injector swap to see if it fixes the problem - at 2 hours of labor, which is 200 additional dollars. If the injector swap fixes it, then it's the injector that's bad. If the injector swap doesn't fix it, it indicates that I need a new DME.

Thoughts? I can replace the alternator myself, but I have never worked with the injectors before, and I don't have confidence that I would be able understand error codes from the ECU. I am tempted to pay them to swap the injector and then find out at least if I need a new DME or not. - update - I am having them do the injector swap to let me know what the issue is. I'm gonna do the alternator myself.

The shitting thing is - if I need a new ECU, then I would most lilely have to order another EAT chip. My question: how expensive / hard to find are used DME's? 1991 M50.

[Bill R.]

same thing Ross.



like I said it's inconcievable to me how this would be a direct result of reversed polarity, even if the starter had been engaged I think it would just merrily spin backwards.

[repenttokyo]

like I said it's inconcievable to me how this would be a direct result of reversed polarity, even if the starter had been engaged I think it would just merrily spin backwards.

wouldn't gearing prevent it from spinning backwards?

[Ross]

For a hondo an hour he shouldn't be guessing. Find a mechanic that knows what the f he is doing.
I'd love to collect $100/hr changing parts willy nilly on someone else's nickel until a problem is cured.
Injectors don't know or care about polarity, I would bet this is not the issue. If the car wasn't powered on I also doubt the DME was damaged. Low voltage will do many odd things to these computer controlled cars. I'd get the cahrging system working first.
A voltage regulator includes the diodes, is easy to swap and < $50.
Sorry for your troubles.

[repenttokyo]

For a hondo an hour he shouldn't be guessing. Find a mechanic that knows what the f he is doing.
I'd love to collect $100/hr changing parts willy nilly on someone else's nickel until a problem is cured.
Injectors don't know or care about polarity, I would bet this is not the issue. If the car wasn't powered on I also doubt the DME was damaged. Low voltage will do many odd things to these computer controlled cars. I'd get the cahrging system working first.
A voltage regulator includes the diodes, is easy to swap and < $50.
Sorry for your troubles.


i wish i had more choices when it came to mechanics, but I just moved to this country this summer, and I had this place recommended to my by the BMWCCA.

He's not going to change the injectors, hes just going to swap the non-functioning one with one that works and see if that fixes the issue. If it does, it's the injector, if not it's the ECU. The alternator is putting out 12 volts right now, which should be enough to run the car without creating any issues. I would like to get the charging system working, but at the same time they are asking a lot to do that. It's a shitty situation and I am tempted to walk away from the car. At a certain point, it is no longer worth the repair costs.

[tim eh?]

have you replaced the starter already?

man... i wonder (only wonder man, i wish i knew more so i could help) ... if your negative cable was fried, and your alternator and starter aren't working as before... maybe some of the + wiring/connectors got effed too and are affecting everything. they must be different on your '91... but have you compared alternator output with system voltage (across batt terminals)?

[repenttokyo]

have you replaced the starter already?

man... i wonder (only wonder man, i wish i knew more so i could help) ... if your negative cable was fried, and your alternator and starter aren't working as before... maybe some of the + wiring/connectors got effed too and are affecting everything. they must be different on your '91... but have you compared alternator output with system voltage (across batt terminals)?

starter is already in. I'm waiting for their diagnosis regarding the injector issue, then I get to make the hard decisions. Car runs and drives as is, voltage is about 12.5 with the car running.

[ryan roopnarine]

output stage error implies that will, in most kinds of electronics, refer to an amplifier or...well, lemme put it this way. if somebody felt brave enough to tell me that there were an output stage error and they hadn't swapped out an ecu yet, and hadn't moved one of your confirmed working injector to the problem cylinder, i'd ask them to explain their rationale for playing around with the fuel injector.

ps...after reading the previous posts....reading is fundamental. still, output stage is probably going to be some manner of integrated circuit/transistor et cetera.

[repenttokyo]

output stage error implies that will, in most kinds of electronics, refer to an amplifier or...well, lemme put it this way. if somebody felt brave enough to tell me that there were an output stage error and they hadn't swapped out an ecu yet, and hadn't moved one of your confirmed working injector to the problem cylinder, i'd ask them to explain their rationale for playing around with the fuel injector.

I asked him and he claimed that he has seen a bad injector cause this error before in a similar situation. He actually is going to swap one of my good injectors in to see if it corrects the issue - because he has tested the DME and it shows no other errors. I will find out more tomorrow.

[ryan roopnarine]

the computers on these cars are mediocre longevity wise. i hope that it is your computer.

[repenttokyo]

the computers on these cars are mediocre longevity wise. i hope that it is your computer.

i'm kind of hoping it's just the injector - much cheaper than a used computer from what I have seen so far in my searches online :(

[ryan roopnarine]

you're in the us now, right? i find that even the crappiest junkyards have one or two e36s or an e34 with an m50 regular in it. i don't see why you'd have to pay more than 100-150 for one.

[repenttokyo]

you're in the us now, right? i find that even the crappiest junkyards have one or two e36s or an e34 with an m50 regular in it. i don't see why you'd have to pay more than 100-150 for one.

yes, I am down here now. A question: Can I put ANY DME in, 1991 - 1995? Or does it have to be from a 91?

I suppose changing the ECU also means losing my EAT chip?

[ryan roopnarine]

yes, I am down here now. A question: Can I put ANY DME in, 1991 - 1995? Or does it have to be from a 91?

I suppose changing the ECU also means losing my EAT chip?

mark was helpful with me even before i had one of his products. tell him which number you have, and he should be able to tell you which ones it might work with, or, worst case, which computers will fit your car (but won't work with your chip). I would think you could put a 91-92 525i or 92 325i in there so long as the number was right, as the 93-up had variable valve timing. after you get this info, go to www.car-part.com (http://www.car-part.com) and take a look, many of the listings will have the dme number with them.

[repenttokyo]

mark was helpful with me even before i had one of his products. tell him which number you have, and he should be able to tell you which ones it might work with, or, worst case, which computers will fit your car (but won't work with your chip). I would think you could put a 91-92 525i or 92 325i in there so long as the number was right, as the 93-up had variable valve timing. after you get this info, go to www.car-part.com (http://www.car-part.com) and take a look, many of the listings will have the dme number with them.

thank-you for the help, I appreciate it.

[repenttokyo]

Update again: So they swapped injector 1 with injector 5 AND IT FIXED THE PROBLEM. I have no idea how that is even possible, but the car runs perfectly now, smooth and no codes. This sadly makes me question the garage quite a bit, but the good news is, I am going to pick the vehicle up this afternoon and then replace the alternator myself this week.

Before I replace the alt, tho, I am going to test it out myself and see if it really needs to be done.

Thanks for everyone's help on this. I guess I now know where to not go back again.

[Ross]

So the injector that was bad in one position is good in another?
Perhaps best not to look a gift horse in the mouth. I wouldn't br going back.
Do the regulator, way cheaper and ought to fix the prob.

[repenttokyo]

I replaced the alternator yesterday - everything is running fine now, I don't see any issues so far. I am going back to that shop tomorrow bc they managed to snap my driver's side arm rest so that now it flops down and refuses to catch. When I got in the car, it was flopped back into the back seat. How the hell does that happen?

[Dave M]

I replaced the alternator yesterday - everything is running fine now, I don't see any issues so far. I am going back to that shop tomorrow bc they managed to snap my driver's side arm rest so that now it flops down and refuses to catch. When I got in the car, it was flopped back into the back seat. How the hell does that happen?

Glad you got it sorted out.

Out of interest, how much did an alternater cost? While troubleshooting an ignition issue, I was quoted ~$500 for a 140 amp.

I'm guessing a gorilla leaned on your arm rest. I hope theres a cheap fix for it.

Dave

[repenttokyo]

Glad you got it sorted out.

Out of interest, how much did an alternater cost? While troubleshooting an ignition issue, I was quoted ~$500 for a 140 amp.

I'm guessing a gorilla leaned on your arm rest. I hope theres a cheap fix for it.

Dave

I ordered a 140 amp Bosch unit from BMA. It was around $300 USD, with $100 of that being the core charge, so it comes out to around $200 total. There were also less and more expensive units available, but I went with Bosch instead of Valeo.

When I got the car home after picking it up, I immediately called the garage and asked them what the deal was with my arm rest. They claimed ignorance, then said that there is a pin inside that can snap and to bring it by once the car is up and running, which I will do this morning.

[nirvana19]

Perhaps when they were replacing the starter they somehow unplugged one of the injectors. Sounds stupid but that happened with me on an M30... just had to reseat the electrical connection and it was fixed. I'm no expert but I really don't see how swapping the injectors would fix both. But, at least all is working!

[repenttokyo]

Perhaps when they were replacing the starter they somehow unplugged one of the injectors. Sounds stupid but that happened with me on an M30... just had to reseat the electrical connection and it was fixed. I'm no expert but I really don't see how swapping the injectors would fix both. But, at least all is working!

yeah, I wonder about that too.

[Tiger]

I remembered you told us they were working on the injectors first... then I guess they worked on the starter and difn't realize they didn't finish the injectors... So all you fried was the starter and alternator?

[repenttokyo]

I remembered you told us they were working on the injectors first... then I guess they worked on the starter and difn't realize they didn't finish the injectors... So all you fried was the starter and alternator?

actually, they didn't touch the injectors until the car was running, bc there was an injector code and the vehicle was running on 5 cylinders.

I had to replace the starter, several fuses, the battery cable going to the starter and the alternator.