Installed battery backward. HELP!!

[E30lover]

To be honest..this wasnt me lol. I'm not that careless to install a battery improperly.

Im looking to buy this 91 e30(i've been hunting for one and i find one with this problem)

The guys says that he hooked up the battery backward(but never started it with it backward). Then the alternator started smoking so he then switched the battery around and no says the car wont start(obviously). Not sure if i can believe the guy but

What damage can i expect to encounter besides replacing some fuses, the alternator and maybe the starter? Does BMW provide some type of idiot-proof things in the car(besides fuses) to protect the electrical system IN CASE someone does install a battery backward?

Im hoping that the ecu isn't fried but if it is, how much can i expect to pay for a 91 325i automatic ecu?

Thanks
Jon

[StereoInstaller1]

Jon, about 10 inches in front of the battery you will find a plastic cover. Remove it, and you will see there are 2 wires coming from the battery...one large wire and a much smaller wire. Follow the smaller wire just a couple of inches and you will find a "fusible link" which is what has toasted.

HTH!
Luke

[E30lover]

ok thanks. but just to clarify, he also says that the alternator was "smoking"(i'll have to go by his word on this) so most likely some components of the alternator were fried..

thanks stereoinstaller1, i've been dying to pick up the e30(one without the chrome diving board) but this problem came up. just wondering how sure are you that the "fusible link" is the only problem?

thanks.

[E30lover]

also btw, how would i go about replacing that? i'm looking for replacement options and its just a wire?

I read that those wires will be destroyed if a large amount of electricity or so passes through it..is that the one?

Anyone know where i can find a replacement or use to replace it with?

[Rocla]

ok thanks. but just to clarify, he also says that the alternator was "smoking"(i'll have to go by his word on this) so most likely some components of the alternator were fried..

thanks stereoinstaller1, i've been dying to pick up the e30(one without the chrome diving board) but this problem came up. just wondering how sure are you that the "fusible link" is the only problem?

thanks.

Diodes in alternator are most likely fried also. Once you replace the fusible link, the alternator light on dash will stay illuminated dim at all times, even with no keys on ignition if the diodes are bad.

There is a slight possibility to ecu damage also.

[E30lover]

situation update

okay. recieved an email from the seller saying that without changing the battery, all the lights work but wont crank...

i now have a feeling the ecu is fried due to it not cranking. maybe i dont know what i'm talking about cause i am no mechanic.

he said that w/o changing the battery, the lights worked but no crank..would the battery still have power? i would think that the battery got drained messed up(again idk im not a mech.)

i havent seen the car yet but im planning to see it soon but just wanna see how much information i can get of it before i go to diagnose it myself.


with that being said, any other ideas/info?

[Rocla]

ecu is fried due to it not cranking.

No, you can't say if ecu bad by that.

Most likely the fusible link or battery, you must repair other damages to find out if ecu is gone.

[E30lover]

okay so before i assume, i'll check it out.

also,about the battery...wouldn't it have been drained or what not if he did connect them incorrectly?

im gonna be checking out the car in a few days. i know a few things to check out is the fusible link and battery. anything else? will i have to replace the alternator right away? also with the fusible link, will i be replacing the whole wire or just a fuse?

sorry for all the long questions. i really want to get this car but wont be able to if its a major issue.

thanks

[E30lover]

ok i checked napa for a fusible link replacement and they have universal ones..but which one should i get for the e30?

they have this one here
in a few different gauges ranging from 14-18(which gauge should i get?) for about $4

or they have this one here for about the same price

which one will i be buying and how will i be installing these? will i be soldering these in?

i also saw this picture of an e34 fusible link is this what i'll be looking for? or will it be this

[E30lover]

okay well im gonna be taking a look at the car today. im bringing a fusible link like the one in the pic right above this post, some wire strippers, electrical tape, flash light, my dads battery from his MKIII supra, and a voltmeter.

Anything else i should remember to bring?

Anything else anyone want to add that can help me in my quest to buying this 91 e30 325i? Anything in general to check out? All advice given is greatly appreciated

Thanks again

[Mossman]

bring jumper cables incase supra batteries terminals aren't the same or it doesn't fit, there are a lot of different battery sizes, but to be fair the e30 has a lot of room down there.

Set a price with the seller before you start working on it. Look him in the eye and shake his hand, after you fix it he really doesn't have to sell it to you so make sure he isn't a sleazebag. If he his lowball him, make a deal, push the car down the block and work on it there.

[E30lover]

haha thats what i was planning to do. he wanted an even grand(cause supposedly the interior is in mint condition and could make an easy $500 selling it but i think thats for me to judge) but i was able to lower it down to $800. my dad says that the car should crank AT LEAST. if it doesnt crank with a better battery in it, then most likely something else is wrong with it. but again hopefully its just some fuses, the fusible link so i can just drive it home and work on it more there lol.

But yea thanks for the heads up. i'll make sure he doesnt flip things around on me(maybe sign a contract of some kind) and hopefully i take home this beautiful e30 :D
wish me luck

[E30lover]

btw, does anyone know what gauge wire i should opt for when i buy the fusible link? Will different gauges determine different amp. ratings? I have no clue with electronics but i will look into it more

[E30lover]

oh and also, the vehilce is a 1991 bmw 325i...will the battery be in the trunk or in the engine bay? not familiar but my dad had an 85 525 and the battery was in the engine bay but i've heard the ones in the e30 can be in various different places.

[n3nyongmini]

battery in trunk.

FWIW, an ECU, alternator and a starter could all be sourced here for prolly less than $200, maybe less. But none of that may be bad anyway.