I recently installed outdoor low voltage lighting. It worked fine for about a week, then it would not come on. I verified the transformer 12v output with a voltmeter. I disconnected all lights and verified the voltage again at the end of the line. But when I connect a light (any one) the voltage goes to zero, and there is continuity between the wires. It seems to be a short, but how ?

Hi, not sure if this is okay to ask this question under this topic but Lefty was of such help with our last problem thought it wouldn't hurt. We have a home alarm that was installed when we had our house built 9 years ago. Today it suddenly armed itself and when I put in the code it wouldn't turn off. Then when I opened the door it started the siren going off outside(actually the siren is in the attic, but is really loud outside)We couldn't get it to turn off, so we had to turn it off at the fuse box. Which of course turned other stuff off in the house. So my husband disconnected the back up battery and unplugged the main plug for the alarm from the outlet the people had wired it to. Turned the fuse back on and everything else works now. But not the alarm, of course because it has no power going to it. What could be the problem and how do we fix it. Is there some way to ck it to find out the problem. Thanks for any and all help with this, its very appreciated.