troubleshooting alarm won't disarm carbin

I have a Magnadyne Carbine PLUS-4600 alarm installed in my Civic 2001. I recently installed a 3rd party head unit in the car and the alarm started to act really strange. The alarm will not disarm and the LED light indicates that it's active. I tried a different remote and it still won't disarm. The only thing I could do is either remove the battery to stop the chirp or remove the battery cable. I tried also the valet trick, which you set the ignition to on and then flip the valet switch to ON and wait for the chirp, which never came. I tried putting the stock radio back in but it doesn't do anything, I was thinking it was possibly some anti-theft mechanism that was set up to the stereo and if it didn't find it, it would trigger the alarm. Currently, I have the cables that plug into the main alarm unit unplugged, so I can drive the car without the alarm going on. One strange thing is that when I do plug the alarm back in, the chirp sound is not that loud, it's like a bit faint and doesn't sound normal. Does anyone know what could be wrong with it? Is the alarm malfunctioned or do I need to readjust something, since I swapped out head units?

the alarm ground could be lose. if the ground is lose the alarm sounds really low and the remote would work right. they that firstConfidence is the key to any project!!

x 2 with Pitt try a DMM across the + and - connections for a voltage check or find the alarms ground and power wires to see if they are secure.