alarm install = dead battery

Got my Autopage 855 installed last night, with the exception on the tach sensing wire and neutral safety switch wire.  This morning, I pulled my truck (2002 Ranger) into the garage, hook up the siren, and go to start the truck.  Nothing except clicking.  Battery voltage drops like crazy when I try to start the truck.  Jump will get it going, but even after it runs for a while it doesn't have enough juice to restart.  I replaced the battery ( which read 419 CA max when it should be 540 CA) an now everything seems fine.  I diode isolated the door triggers, I don't know what could have killed the battery.  I'm hoping it was just coincidence 'cause otherwise I'm stuck.  Any ideas?  Thanks!

Well maybe you just left your driver door open too long while doing the install with the dome lights on. That happens to me alot , especially on the Ford expedtion and navi's too many dang lites.LOL

I had the neg on the battery disconnected for most of the time.  I'm at a loss as to what else it could be.  I pulled both fuses for the remote start wiring, I'm not using the remote start yet.  I have the door triggers wired, and they are diode isolated.  Could I have done that wrong, I didn't think the doors would lock/unlock if it wasn't correct?  The hood pin is connected, along with the instant trigger, but they are both diode isolated also as per the manual.  The only other place I have wires hooked up right now is for the parking light flash relay.  It is connected per the manual as well.  Is there any way for the battery to be discharging throughany of the remore start wiring even with the fuses disconnected?

I cleaned the battery terminals really welland they were tight.  That was my first thought.  I had installed the starter kill relay, but after it didn't start I disconnected it thinking that was the problem.  It is currently NOT installed.

My thoughts exactly.  It is 3 years old, but 70,000 miles.  The tester at the parts house said it was really low cranking amps.  I hope that is what the problem is.  My truck starts better now than it has in a while with the new battery.

hehe happened to me when i was in the process of installing my remote starter battery swelled up and was dead... prolly of a combination of old age and starting so manytimes to test things but oh well