how to disable factory car alarm

A 1989 Prelude does not have a factory alarm..somebody evidently put in an aftermarket one, so you will have to find out what brand and contact the manufacturer

how do you like them beans?

Trace the wire coming out of the alarm box. The red wire is usually the power and there should be a in-line fuse. Remove the fuse.

I know this is old, but I just wanted to correct it. 88-91 preludes DID have a factory security system, all be it rare. The control box is located in the trunk under the rear window. To disable it all you have to is unplug it. To use it without the remote, just flip the switch on the side to manual, it will activate and deactivate with the drivers outside key lock.

Last answer sounds good if the alarm is indeed a Honda original. If not, and this could be the case...most alarms have brown lead which can be grounded to reset/program an operating key fob. Find the brain-box under the dash to the left of the wheel column...and confirm the brown lead. With the key on...that lead to ground should disarm. Then you can often unplug the aftermarket alarm (main harness) and that should be that. Good Luck, and let me know!