Dome Light - Alarm Trigger Relay
 

Installed an alarm in my 1994 Jeep Cherokee. I have a question about installing the dome light to the alarm. Today, I pulled the door trigger apart and noticed two yellow wires and one black wire. The question I have is what is the best method of using the dome light trigger to the negative alarm module. Using a relay how do I determine which wire is the negative?

87 - Yellow Wire (which one of the two)
86 - Negative dome light wire to alarm module
30 - Ground
85 - 12V - Constant
87A - Not used

Any thoughts would be much appreciated. Thank you.

Bust out a wiring diagram, the pin switch when closed may just ground to the chassis.