I tried to start the rover and it clicked dead like the battery was dead. Then I try it again and nothing. The light won't even turn on. Then I let it sit try it again, the lights turn on but when I try to start in everything goes dead. Alternator? Starter, or some silly fuse.

 

Jiggle the battery cables, might be a loose connection.

 

Now I feel silly. I tighten the cable and it fired up.

 

When conditions permit, remove both battery cables and clean battery posts and cable ends (especially the "inside" mating surfaces) with a small metal brush or fine sandpaper. The loose cable will have built up corrosion and oxidation, and problems could return. Some guys coat the cleaned battery terminals with a thin layer of vaseline after tightening.

 

Last weekend my son left the lights on for a couple of hours and when we returned to the car the battery was DEAD. Not even a sound and/or light when the key was turned. We hooked up a jumper and after a minute the alarm started sounding. A couple of manual locks/unlocks with the key solved that. Eventually the battery took the charge and the car started (and started again later without a jump).

So the question I have is.... did the alarm immobilize the car after the battery had died past a certain point? Or was the battery just so dead as to provide no power (not even a weak attempt) to the starter at all?

 

No. The alarm remembers that it was armed when you brought the voltage back up by attaching jumpers. The hood was open, so that switch triggered the alarm. If having to jump off, always hold down hood switch with something before jumping.

The truck actually immobilizes every time you arm the alarm, so a thief can't straightwire the system. Each model change of Disco / Rover seems to get more sophisticated alarms that really can cause you a problem if they act up 700 kilometers from a dealer in the Northern Territory of Australia. On my 97, you can hold the key when locking for about 5 seconds, and it will lock, but not turn on the alarm.