06 explorer and viper

depending on where you live (climate wise) you dont always need tach.  You can program the unit to voltage sense.  In most cases you will have to catch tach wire under the hood. (fuel injector wire, ignition pack,) sometimes it can be found at the instument cluster.  The viper install manual explains how to test tach wire.  The hood pin is simply a safety device that is mounted under the hood. It prevents the vehicle from being started if the hood is up.  I dont know what to tell you on your antenna problem.  trace the antenna wire,and make sure its not sliced, punctured, etc. at any point. Also, do those transmitters need to be programmed? I know the brand new Viper 160XVL requires the transmitters in the box to be programmed as oppose to both of them being pre-programmed.  David

MECP Basic Installer Certification

the hood switch is also anouther monitor for the alarm system. this is the by my opinion the most important part of the alarm. if a theif can cut your battery cables your alarm is useless.  a tach signal from the car is always better than a voltage signal. on the 4.0 motor the injectors are easily accessable, i also think that the coils are easy to get to.