Voltage for ignition sensor
 

I recently installed in a plane a MLD35 gas engine that I have had NIB for some time.

The ignition module said that it was good for up to 8.4 volts, so needing some weight I used a 2500mAh 5 cell NICAD that I had to hand.

Took the model out to do some tests, the engine started easily and ran well, however I was getting some interference.

When I got the plane back on the bench to investigate I found that there was no spark. Further investigation indicated that the problem was the ignition sensor (I had a spare that I was able to substitute, when I did the spark was back!)

This started me thinking that maybe the module itself was able to handle the higher voltage but not the sensor. As it all came together I didn't give it a thought when I first installer. As the sensor is just a hall device with maybe a transistor I would not have thought it was that sensitive, but who knows. Certainly before risking my spare I will be dropping back to a 4 cell pack.

Anyone any thoughts?


Terry

I guess I might have blown it as well? I would also assume if the engine were supplied with an 8.4v ign. module, that the sensor would accommodate as well....

My guess would be that your plug cap is not on correctly. This may have been both the cause of your interference and the sensor failing. The interference would be RF leakage caused by an arcing loose cap. The sensor going out would be the cap provides the ground. A poor ground can fry a sensor.

My recollection was that the cap was on firmly, but something to bear in mind for sure. The motor was running OK when I packed up for the day, it was only later back on the bench that I discovered the module was kaput. Thanks for the feedback.

Terry

You might want to do some searches regarding the MLD ignition. IIRC, the problems described were fairly common complaints when the engine was being sold. If it were mine, I'd just replace the ignition and sensor with a new Rcexl or Rcxp and be done with it.