The job of the manifold heater is to help vaporize fuel in the intake manifold when the engine is cold. This will help with cold starts and idling until the engine is up to operating temperature. This kit allows a manifold heater to be used if you are rewiring your Jeep using a Painless chassis harness, using a later style manifold on an older Jeep, or if the factory relay was cut from your Jeep at some point in time by you or a previous owner.