viper 350hv, 2002 dodge cummins 2500

I'm having trouble installing my 508d to my Viper 350Hv. I've been searching the forum and Internet with no success in solving my issue. 2002 Dodge Cummins 2500 I've been trying to tap the 508d into the H1 harness. Well, when I tapped the blue/pin 6 it was a negative signal. After a few trials of the sensor the blue wire now shows to be positive. Why would the blue/Hood or Trunk negative pin first be negative as per manufacturer then be positive? I can't get an instant trigger now because the 508d doesn't recognize the signal? Been at it for a few hours, please help!!

Often times a wire will show positive on it until it receives a negative signal to trigger the alarm. The blue wire doesn't actually give out a signal, it waits for a negative trigger from a trunk, hood, or sensor ground. You can place a diode with the band facing the 508d and reconnect the wire to the harness. That way, the 12v backfeed stops at the diode and only the negative signal from the prox sensor goes thru if triggered.