automatic headlights set off alarm

I am having a problem with my 727T Hornet that I  installed.  When I stop the Truck, 2003 F350 FX4 6.0L, at night when the headlights are on, and arm the alarm, the alarm will sound when the automatic headlights turn off.  At night, they remain on when you shut off the vehicle for a bit of time.  When they shut down, this causes the alarm to trigger.  Obviously, this only happens when the auto headlights are on and if I wait for them to shut off before arming the alarm, it is not an issue, but this is not always convenient.  Any way to bypass whatever is causing the alarm to go off?  Please advise.

The first step will probably be to know which "zone" of the alarm is being triggered. That is, the alarm usually has various inputs to be connected to the car's doors, trunk, hood, shock sensor, and so on. Each one of these inputs is called a "zone." I've seen a 727T before, but never installed one. Anyway, it generally goes like this: 1. Perform the necessary actions to make the alarm false. (That is, in your case, arm it with the auto headlights on.) 2. Wait for the alarm to false, then disarm it. 3. Without turning the ignition on, observe the red LED drilled into the dashboard (the LED for the alarm). It should be flashing a certain amount of times, over and over. 4. Post here how many flashes you're getting.

It's not voltage sensing is it? (Or have they finally discontinued voltage sensing?)

I'm thinking either: 1. It's an old-style voltage sensing unit. That is, whenever the battery voltage changes, the unit assumes the domelight has been activated (by a thief opening the door). Maybe the lights shutting off makes the voltage change enough to trigger the alarm. OR: 2. Maybe the automatic headlights have a relay that's in a location very close to the alarm's brain. When the relay clicks off, the alarm senses the vibration and considers this a shock sensor event. Maybe try rolling the windows up and park in a very quiet environment. Let the auto lights time out and see if you hear anything.

I never like voltage sensing units - too unreliable. And I thought why not use the switch that triggers the light (voltage drop) instead - that way the alarm might work on my mum's car - she always turned off the door-triggered dome light doe safety reasons).     But I think they were discontinued due to the number of modern accessories - as if the old normal instantaneous battery fluctuations or motor-wound spring clocks weren't problem enough. The two things I would always disable on an alarm - voltage and shock (window breakage) sensing. And yes - glitches resulting from spikes etc in nearby wires. They could effect both voltage sensing as well as "raw" switch inputs that were not properly decoupled (ie, a small cap to suppress radio interference etc). My only two false trigger issues: a car alarm off door switches (decoupling caps), and on a domestic alarm - cold wind down wall cavity through PIR cable hole - fixed with plastitac/putty to seal the cable entry. But remember - I'm not an installer. (But I have advised & solved many installations, and defeated many more.)