How to stop Horn alarm?

[trane294]

I have 525i 91. I am not sure what happened. It was working fine and then I put different battery. I put it first time wrong direction - to + / + to -. Idk if this did smth but when I put it right way by horn alarm just going crazy. It seems the same issue like I found here (911 Horn wont stop blaring). And that exactly whats happening when I plug the battery in youtube.com/watch?v=hMeYwlyggX8. Im not sure if I just need to cut this alarm?

https://www.youtube.com/watch?v=hMeYwlyggX8

[bimmer@15]

Its a security system, connect the battery then stuck your key in the drivers door and turn it, i cant remember if you need to lock it or unlock it but just stick it in the lock cylinder and turn it bolth ways and it should stop

Sent from my LG-US998 using Tapatalk

[trane294]

Its a security system, connect the battery then stuck your key in the drivers door and turn it, i cant remember if you need to lock it or unlock it but just stick it in the lock cylinder and turn it bolth ways and it should stop

Sent from my LG-US998 using Tapatalk

Have tried. Didn't help

[trane294]

So I unplugged on-board computer and car stopped alarming. It starts and everything. When I plug it in nothing shows up and it just starting alarming again

[bimmer@15]

I know that some obc can have a pin used to disable the car, maybe its that

Sent from my LG-US998 using Tapatalk

[fo3]

Yep, the OBC can have a security code to set of the alrm/horn and disable the car. Best guess is that's been fried if the problem started after connecting a battery wrong. Isn't the coding plug for the whole system supposed to be plugged into the back of the OBC or somewhere in the dash wiring? Maybe that system is damaged also?

OBC manual: http://www.mediafire.com/file/cx0z1z..._info.pdf/file

It says there if you disconnect the battery and try again there should be a count down timer of 15min then after that it's reset.
After that maybe it's permanently disabled? It wasn't clear about that, it just said for emergency start if you don't know the code: disconnect battery 1min, then reconnect and put up with the horn for 15min and then you can drive! LOL
If there's no ODC display then consider it toast I guess.

E: Also check shoguns link: http://bmwe32.masscom.net/johan/obc_...c_secrets.html
and the owners manual about the OBC alarm http://www.mediafire.com/file/eifibe...anual.pdf/file

[trane294]

Thank you guys for your help. Yeap I have a feeling that its fried. I have 2 other E34 that I can try to plug in their on-board computers. Will they fit or you gotta have exactly same year production one?

[shogun]

If they are identical, they will fit, there were OBC III (earlier version) and OBC IV.
Or just disconnect the alarm horn, that is in a different location than the normal horn. On my E32 the normal horn is behind the kidney grill, the alarm horn is on right side next to the windshield wiper mechanism, difficult to access.
Antitheft Horn H1 is located below right hand fresh air cowl.

[Singing6]

I know I am late to the game, but I have seen this failure before. There is a relay on the later cars that is part of the loom for the remote key fob module that is under the back left seat. This relay dangles into the battery well under the back right seat. In my case, I was working with a car that had sunroof problems and the battery well would fill with water. This shorted and then corroded the internals of the relay, to the point that it would stay shorted when the water was drained. Unplugging this single relay solved the problem.