horn goes off when battery connected?

[csp23]

'88 535is

This car had been sitting in my garage for over a year until today. While installing a new battery - old one was removed when the car was parked - the horn near the battery would go off everytime I connected the battery. I removed the horn for the time being and it is still out of the car until I can figure out why it was going off. The regular horn is still installed and operational at this point. My guess is it has to do with a factory alarm or something?

Anyone know what I should do to be able to install this horn back in the car without it continuously going off?

Thanks.

[Blue Shadow]

That is the OBC alarm horn and this indicates the OBC control is bad. You need to change the black box under the dash outside the steering wheel. A junkyard part should work fine. Probably a relay stuck in the box or something. Well tha tis my guess, anyway.

[DGM Calgary]

Either that or the horn relay itself is stuck. Swap that out for a quick way to eliminate one possibility.

[Blue Shadow]

The OBC horn relay is inside the OBC relay box. So it would be the box.