rear defroster 2001 Grand Prix

I checked the polarity of the white defroster wire and it is negative but the multimeter doesnt ground to 0.0 when I press the defroster button. So my question is would it be safe to hook up the defroster to the -200 mA of the Viper 771xv using a relay as followed?

86 : 12 Volt Constant

87 : Ground 85 : Alarm input channel 30 : white defroster wire87a: not used

As long as you are sure that it is a negetive trigger then that relay setup should work fine. Alot of times a DMM will not read a perfect ground when the switch is turned on, even if it is negetive. Check it using Continuity and Resistance, but just be sure that its not switching to a positive 12volts or you could have a fire. Either way just use an in line fuse just to be safe.