FAQ:Runaway Locomotives with Lenz DCC Systems

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A runaway is a locomotive which will not respond to commands. It may accelerate from a stop or not respond to throttle commands while in motion.

The usual cause is a corrupted DCC signal, which forces the multifunction decoder to change from NMRA DCC Mode to an alternate power source, which in many cases is Analog DC. The decoder responds to the track voltage by maximum power to the motor.

Some Lenz DCC systems, when powered by an AC power supply, may have runaway locomotives during the power-up sequence. This is caused by noise in the AC power being applied to the track during the command station's boot up sequence, which causes a runaway. The internal DC power supply allows the noise to pass through.

Some Lenz owners will add a toggle switch between the booster output and the track to allow them to disconnect track power until the system is up and running.

Other systems may also exhibit this issue if they lack the ability to switch track power off.

For a Lenz DCC System owner, investing in a quality switching power supply which provides clean DC power will help eliminate this issue. This is true for other systems which also use an AC supply.

When selecting a power supply, as always: Read the manual for the correct voltage and current required.