Sparrow / NmG
Many Sparrow motor controller failures have been in part due to overheating. If one wishes to prevent this, one can install additional fans to get more air over the motor controller.
My Sparrow (#220) came with one fan aft of the motor controller, blowing air over it. This picture shows an additional fan installed forward of the motor controller, sucking air over it. In the picture, the motor controller has been removed, which makes seeing the fan easier.
P.S. This modification, which I documented on this wiki some time ago, was not sufficient to keep my motor controller from self-distructing.