To RUN the burner, or provide a lockout when the engine is off? You don't want to run the burner off the engine wiring.
Hotsys and Ramteqs tap the AC current coming off the alternator, and run it through a bridge rectifier to trigger a relay that feeds battery voltage to the burner. If the engine isn't spinning, there's no voltage and the burner won't run.
Got a wiring diagram of the burner?