Door trigger from dome light

I'm trying to setup the door trigger for an Autopage 855 on a grand cherokee.

The courtesy light has 2 wires both are hot (12V) when the light is off, when the light comes on one drops to 0.2V the other stays at 12V.

Is this normal? I connected it with a relay to the + door trigger. This setup seems kinda wierd to me any better ideas? Am i screwing up somewhere?

TIA..

what year is your cherokee?

yes this is normal.  The courtesy light is called a negative trigger...that wire goes to ground when the light is on

Depending on your unit it may have a postive or negative or both input triggers....if it has the negative door trigger / pin input just wire it straight up.  if it only has a positive input then wire up a relay to change the polarity.

Does your door trigger sound the alarm when you arm it and open the door....?   If so you must have wired it up correctly...

I have + & - trigger on the 855 but I cant get it to alarm on the - trigger. I am using a relay on the + trigger side. The relay is on when the light is off. When the light comes on the relay relaxes and the alarm sounds. Is it OK to have the relay always on like that?

If that is ok, the only thing I have left is the problem with arming the system before the dome light has shut off. Any idea on how to make the alarm ignore the light for the first minute after arming ?

Thanks

I have switched it to use the - trigger through the relay as described by JWorm but opening the door does not set off the alarm. Maybe the - trigger is bad? If the alarm is active and i ground the - trigger wire should it get loud?