2000 explorer rear defroster

Just installed a remote starter on my 2000 Explorer, and would like to hook up the rear defroster to work when the option button is pressed. Does anyone know which wire I should use coming off the switch, and is it negative or positive? Thanks

Do you have a volt meter?

Yes I do?

You need to get to the harness that is connected to the switch.  There will be at least 3 wires on it.  Ground the black lead of your meter.  Set it to DC Volts, or to the 20 Volts DC scale if applicable.  Touch the red lead to the first wire in the harness, notice the reading.  Now turn the defroster on, notice if there is a substantial change in voltage.  Do the same with the rest of the wires.  Post what you find.    Next connect the red lead of  your meter to a known power source, leave the meter on the same setting,  now touch the black lead to the first wire, notice the reading, turn on the defroster, notice reading again.  Repeat for each of the remaining wires.  Post your findings here.