so it's most likely a voltage change that is setting off the alarm.

Current sensing alarm?

I should have said current change, of course, as you pointed out. That's how the alarm knows the doors are being opened -- the current drawn by the dome light is enough to trigger the alarm. I'm not sure what the threshold for the alarm is -- how many milliwatts it takes to trigger it. Maybe I can find out. The alarm senses the current draw by means of an inductance coil wrapped around the positive battery cable -- you wouldn't think it could be too terribly sensitive. There is no adjustment on the alarm for sensitivity to current changes -- I can only change its sensitivity to motion.



tanstaafl.

"There Ain't No Such Thing As A Free Lunch"