Spark Switch Cycling

  • I am using a Powerbox Spark switch in my Comp ARF P47. The spark switch is employed to turn on both the APS 380 fuel pump as well as the ignition to the Moki 250 radial engine. Everything was working great through the first 11 flights. However, on the last flight something happened I still do not understand. About half way through a normal flight time the motor began to run very roughly seeming as though it had lost a cylinder (or two) fortunately we were able to get it down before the motor stopped all together. We were at a large show in Canada so we got it off the runway tuned off the aircraft and the transmitter and began to push it to the pits. As I was rolling it back I noticed the ignition indicator light was flashing on and off at about a 2 second interval. When we got back to the pits I could then hear the fuel pump was also being turned on and off as the indicator light would indicate. Again, this is with the power to the Rx and Tx OFF. When we opened the aircraft up to remove the ignition battery the Spark Switch was VERY HOT! Not melted but really hot to the touch. When I returned home I plugged in the ignition battery, turned on the radio and the unit seems to be operating normally. What I need help with is what will make the switch cycle like that? Over current I suspect but the fuel pump is rated at 800mA max and the ignition at 900mA. Not a huge amount of head room for a 2A output but interested to hear your thoughts on the cycling and the configuration. Thanks!

  • Hello,

    I´m pretty sure it´s overloaded. The 800mA for a pump is not a very reliable value. It´s much more if the pump is not fully "open" on the output, which never is in a gas engine. The valve in the carburator is almost close in runtime which creates a certain amount of pressure.

    You can use a regular SparkSwitch for the pump + SparkSwitch Pro for the ignition and telemetry