Stray current??
in General Tech Discussion
9 months ago
Any suggestion appreciated for suspected engine electrical issue! 1999 Rans S7 with 912ULS with 800 hours TT, 120 hours in last two years. Since owned, radio is unusable due to engine and strobe static.
With engine off, transmission seems normal; reception is slightly weak but clear. With engine running, transmission and reception are weak and covered by engine and strobe static. Most recently, the static turns into a loud squeal after five minutes of idling. Interesting that I have the same problem with a handheld radio attached to nothing but a headset!
One intermittent problem is half-range fluctuations of the tach, altimeter, or ASI. The altimeter and ASI have no electrical connection other than ground to panel. Also recently, the battery tender light occasionally stays solid red (less than 80% charge), even though the voltmeter says 13V. Usually I plug the tender in during preflight and the light blinks green (greater than 80% charge) for 10 minutes before solid green.
In attempt to rule out ground loop or bad wires/ground, things done with no effect:
*checked all visible wires for voltage or resistance; including voltage regulator, stator, intercom, radio, jacks, lights.
*installed positive and ground buss bars, with ground buss and battery cable attached at engine mount
*cleaned all grounds
*replaced voltage regulator, capacitor, and noise filters to radio and strobes
*replaced antenna cable with new, radio and antenna with used, and tried multiple headsets.
*removed separate ground wires from the battery to the radio and strobes installed by an A+P fifteen years ago for "radio static"
Engine still runs well other than minor vibration less than 3000rpm, carbs are balanced. Flight time is still fun as long as I don’t need to communicate with anyone!
