Constant Speed Not Constant

[RV6-O540]

Cant believe it coming up on a year since my original post on this issue, but the problem actually turned out to have two answers and I thought it might benefit someone.
As several of you guys suggested, in less than 10 hours the prop governor failed during a prop cycle on run up. I was just happy to finally have the answer so I re-installed it, after factory overhaul, only to find the exact same problem on my test flight. Since I knew the governor was OK and it was probably an electrical issue I just lived with it through the fall and winter without much time to chase it down.

Im using a Vision Microsystem (now JPI) RPM transducer on a Bendix Mag feeding a GRT system. The JPI guys gave me a couple things to check. Found two issues. Transducer wire running next to the standby alternator output wire could have been interference. Then two of the leads with worn places touching the alternator case. The transducer wire coating seems very thin, almost transparent. Didnt take much to rub a hole in it. Rerouted, shrink tubed each wire, flew it, works like a charm. Nice and stable.

So by coincidence the prop governor failed just about the time I was having RPM sensor issues.

Just wanted to pass on the results and thanks. One of those little victories over electrical gremlins that made my day.

[rvmills]

Thanks for the follow-up Bill. I have a VM-1000, and that instrument has some movement in many of its readings. It typically cycles between small steps in its readings, so I always wrote it off to the display. Always small movements in digital readouts, more nuisance than anything, especially when testing and taking data. However, based on your report, gonna have to inspect my transducer wire and that coating. Good info!

How's that Super Six running'?! Recent pics?

Cheers,
Bob