adding sensor to oem ford alarm

All the doors/hood triggers on the Explorer rest at ground when closed, so your last measurements are correct. In order to hook up an external sensor you need to "open" or "break" the wire while your sensor is tripped. I usually would use the hood Pin wire and break that wire open with a relay. So the output of your sensor needs to be hooked up to a relay. not directly to the hood pin wire. One end of the hood wire goes to 30 of the relay, and the other goes to 87a. Wire your relay for Constant 12V(86 on relay) and Ground(85 on relay) off your sensor output. When sensor is tripped the relay will open the hood wire, this will fool the factory alarm that the hood was opened and go off.

flobee4 wrote: All the doors/hood triggers on the Explorer rest at ground when closed, so your last measurements are correct. In order to hook up an external sensor you need to "open" or "break" the wire while your sensor is tripped. I usually would use the hood Pin wire and break that wire open with a relay. So the output of your sensor needs to be hooked up to a relay. not directly to the hood pin wire. One end of the hood wire goes to 30 of the relay, and the other goes to 87a. Wire your relay for Constant 12V(86 on relay) and Ground(85 on relay) off your sensor output. When sensor is tripped the relay will open the hood wire, this will fool the factory alarm that the hood was opened and go off.

HA!!! I love it!  I thought it out this morning and tried it this way ^^^ before reading this. It works perfectly!