what to fix when Battery installed Backwards.

[Mario32r4]

Hi. I have a 1998 E36 and I have no idea where to start the fixing process.

What happened is that while replacing the battery I accidentally plugged the battery backwards.
I pluged possitive cable to negative side of battery and same with negative side. When I did it, the battery shoot out sparks and a burned rubber smell came out of the trunk area (where the battery is located) and the same odor was found near the fuse box under the hood at the front part. Also the metal of the negative post was really hot, but not the same on the possitive post.
One of the rear windows rolled down by itself so, I plugged the battery again but this time correctly. Nothing happened when I did this. I rolled up the window with no problem and all the interior lights on the car work perfectly.
I plugged in the key and even the dashboard lights up on position #2 but the engine just wont start, It does not even make a single click or sound.

Where should I start the Fixing process on my car. This is my first car and I do not have much knowledge on the subject.

[Okin]

Check all fuses and relays?




Hopefully you didn't fry the computer.

[flyfishvt]

Yeah I would check all fuses but I would go one step further. Take the screws out that hold the part the fuses actually go into and look under the fuses for burnt wires. You probably toasted a bunch of fuses so it wouldn't be a bad idea to replace them all and keep any good ones for spares.

See if the car will start after you've checked the fusebox out. You may have fried the battery too. Don't be surprised.

You probably melted some of the insulation off the main battery cables. If you're very lucky it was just the ground strap cable. Any wires that melted could be causing a dead short so you'll have to do a parasitic drain test to see if that's happening.

Here is how I would approach it. 1) check the fuses 2) check under the fuses for burnt wires 3) Pull the carpet out of the trunk and look for burnt battery cables 4) hook up the battery and do a test for parasitic drain. 5) see if the car will start and keep your fingers crossed.

[Joylove]

If you are lucky there may be a thumping great protection diode that has burnt out. Check the E36 PDF schematic. If not you may have done some serious damage to almost everything.

[Mario32r4]

I checked all fuses, none of the fuses are fried. But I can't tell if the big square relays are also burnt.
Also, I do see one of the cables under the fuse box to have the plastic peeled off.

[flyfishvt]

I checked all fuses, none of the fuses are fried. But I can't tell if the big square relays are also burnt.
Also, I do see one of the cables under the fuse box to have the plastic peeled off.


But will it start?

[Mario32r4]

No it will not start at all.

[flyfishvt]

Do you have a bentley Manual? Do you have a decent multimeter and do you know how to use it? You will need both as you wade through the maze that is ahead of you. It will help all of us here if you at least had a good working knowlege of how to use the multi meter.

Did you inspect the fuses or did you actually pull themout and test them?

[RNeil]

The diodes in the alternator were destroyed. They are not protected by a fuse, so the insulation on the wire to the alternator was melted. You need to look at the whole length of the wire since the part that is in a bundle is more prone to melting. The two battery posts had the exact same current, but the negative got hotter because the connection resistance was higher.

I am not saying that there is not more damage.

[chapellej]

i would definatly say you have fried your computer, you have not spark control or fuel as well as the alternator.

1. get a used, working ecu and swap to eliminate that, most pick and pulls will allow you to return them for a credit or full refund.

2. replace alternator and wire's.

3. repalce battery for sure, you may have damaged the battery as well.

4. check starter wires as well.

5. use a digital multimeter to check continuity on the relays.

6. pray to god you have not blown wires under your dash other wise we'll see your car for sale in the part out section.

[lBMWl]

"what to fix when Battery installed Backwards."

THE MECHANIC!

do you have automatic or manual...... just traced out both.... switched power goes to a neutral safety switch (automatics) and a clutch pedal switch (Manual) f you fried one of those two, you wont get switch power (12v) I wish u were closer, id love to help trouble shoot this one!

[nighthawk328i]

You probably fried the DME, a member on here awhile back had the same issue. His brother installed the battery backwards and it ended up frying the DME. If I recall correctly, the only damage to the car was the DME. This was on a 328 though. Since yours is a 318 i'm not sure. On the 6 cylinder 96+ there is EWS so if you replace the DME you'll need to get it realigned at the dealership. Since yours is 96+ as well I would assume you will probably have a similar process. However, don't just go out and replace it without testing it.

What happens when you try to start the car? Does it crank at all? Did you check the voltage on the battery after you hooked it up backwards? What did it test at?