How can I Block 12v

I am wiring up an alarm and have this minor dilemna. I am using the domelight supervision lead to turn on the lamp when disarming but have a problem of not rearming because the lead is seeing 12 volts. I need to figure how to block 12v yet allow gnd to pass when applied to active the domelight. The supervision lead is connected to a relay pin 85 and 86 to 12v. The 12v is going thru the relay coil over to the supervison lead which is where I need to find a way to block it. A diode will not so now I am asking if anyone has a solution. Thanks

try adding another relay.

i dont really understand... This is what i am getting. You hooked up the domelight as the door trigger, so when the domelight supervision is on the alarm thinks the door is open and will not rearm...??

Insert a diode inline on the door trigger wire and have your door trigger wire on one side and domelight supervision wire on the other. Which side will depend on polarity of wire you are using.

Not exactly. The door trigger is wired to a seperate sense lead. The domelight supervision lead is connected to the domelight wire. When this lead is connected, the domelight turns on during disarm as it suppose to but then the rearm feature will not work because there is 12v present coming from the relay pin 85. Pin 86 has 12v. NOW if I remove the 12v then the rearm feature works but not the domelight disarm feature. Seems I can only use on but not both. I need to find a way to block 12v but allow gnd to pass when applied. Hope this clarifys it a bit.

I could have explained better if you listed what kind of car you have....while we're at it, what kind of alarm?

yup!

on a perfect world once the domelight turns off it should rearm, unless you're using the trigger wire for both trigger and dome supervision. I really didn't get the question.

My last response was for Xetmes but was uable to get back onto the forum for some reason till this morning. I am wiring a Whistler WH-700 alarm to a 1998 Blazer. I have wired the three door triggers with diodes to the door tigger sense lead and do not have a problem there. The domelight supervision sense lead is wired to a relay pin 85. The domelight wire is connected to pin 30 and gnd is pin 87. Pin 86 is 12volts. This setup completely isolates the domelight supervision lead from the actual domelight wire. What I do not want to see 12 volts at the supervision lead coming from 12 volts batt. Maybe this link to the manual helps: http://www.autoelectric.ru/autoalarm/whistler/whistler/whistler-m.htm