no alarm response, other issues

It started a couple of weeks ago. At first, once in a while the alarm wouldn't respond to the remote. I'd try to disarm a few times until it worked. Then it came down to the alarm would disarm (sometimes) but the lights wouldn't flash, the horn wouldn't sound, and the driver door wouldn't unlock (the other 3 unlocked fine). All last week I had no response from the alarm at all. I was out of town this weekend (with my wife's car) and came home to find that my alarm warning lights were pulsing rapidly and there was a relay in the brain clicking like crazy. So now it's unplugged until I have time to look at it. It's in a 1999 chevy tahoe. Any ideas on what this could be or where to start?

Check your main ground to the alarm.  A lot of times they'll get crazy like that when they don't have a proper ground and then it "looks" for a ground through another wire on the harness.  DEI alarms and Remote Starts do this for me when I'm hooking them up, get ahead of myself and forget to connect ground first.   BTW, what kind of alarm is it, brand, model?

880xp It has been working for a few years now so maybe the ground is corroded.