i have factory alarm that came with my 99 accord and it works fine, but the horn doesnt work go off, so when my alarm goes off, it just blinks lights and immobiliszes the car, any suggestions on what to do?

 

If the cars horn works then the output from the oem alarm has been disconnected or the horn output is blown.

You will have to find alarm brain and check the horn output lead, not sure of the wiring on an oem alarm but the alarm brain will have a relay built in for horn output or an off-board relay, should be able to find the horn output with a multimeter. 94