airhorns when door is opened

So when you open the door, both go off, or are you wanting to wire them into the alarm? First you will need a solenoid for the air horn if you are using a tank, other wise you will just trigger the compressor. Now this will only give you a single long tone until you close the door or disarm the alarm. You will need to do some other work to get it to oscillate. Perhaps a turn signal flasher could accomplish this. For the door trigger, you will wire the door trigger to the coils and give them the opposite polarity. 30- air horn solenoid or compressor, 87a- to air horn switch, 87 to polarity that triggers air horn. Your strobes probably take 12v to the brain to turn them on, so again door trigger and opposite polarity to the coils. 30- 12v and 87 to strobe brain. With going to the alarm, you could probably just tie the relays into the siren trigger rather than the door trigger.

So your now adding two more relays to do it cleanly, of you might be lucky and use the door trigger as the ground for the coils and the siren as the positive.