DEI Siren Issue

Hi, I've been working on re-installing a Python 750 alarm and DEI 551t valet remote start in my 95 Chevy G20. It was originally installed in 96/97 but my late Grandma had the system taken out in 99 just before she traded the van in. Ironically we never did re-use the alarm in a different vehicle and I managed to find the van in 2016 and got it back. I repaired all cut wires and all the alarm/remote start functions work fine, I used a new old stock 514T siren. While I was finalizing install putting the cluster back in, the siren started going off, although more quiet than usual, disarming didn't stop it, I even pulled the fuse out of the alarm harness and the siren continued to sound until I pulled the negative battery cable. Any ideas what could be causing that? When I hooked the battery up again it was fine again and siren had normal volume. I didn't add any extra diodes or relays beyond how the installer already had it wired in the 90s,and the ground screw is clean and tight. Thanks

Had the same thing one time turned out the ground for the alarm was not well secured to the vehicle.

Sure enough I think that was it, moving the harness a certain way made it go off, I ran a new ground and it's not happening now.